People don’t realize it, but English is actually one of the easiest languages to learn initially, but perfecting it is difficult. To begin with, we have a definite word order that never changes, but some of other languages change their word order according to the whim of the speaker. Another thing that makes English easier is that we don’t have to match any adjectives in gender with our nouns. Still more, we have very basic verb tenses, and only conjugate verbs, not other parts of speech like some other languages. English is a complication of German, Latin, French, Spanish, and probably a few more It seems that if you are from a European country, English is usually pretty easy for you. English is logical and has specific rules. The hardest part about English is the simple past tense of the verb. Most of the other tenses all follow the rules most of the time pretty well, but people have to study and work at the simple past tense. After that you have learned the simple past tense, the past participle gets easier because many of them are the same as the simple past tense, and you don’t have as much to memorize as you did with the simple past tense. Our reading is difficult because our spelling doesn’t follow the rules, but it is readable even if people aren’t sure how to pronounce it.
I don’t know anything about Russian except the Romanians tell me it is a really hard language, and the Romanians find English very easy. The Romanians said to me about Russian, “They made me study it in school, but they can’t make me speak it.” The people in the Ukraine speak Russian.
As for Japanese, initially, the basic Tokyo dialect they teach foreigners is not too hard for foreigners to master a basic conversation. The hiragana is easy to learn to read because you say it exactly the way it is written on the page. The verbs follow the rules. However, the more you get into Japanese, the harder certain things get. Every area of Japan speaks a different dialect. English is much more universal than Japanese. If you speak English, you can talk to anyone from any English speaking country. However, if you speak the Tokyo dialect, it doesn’t mean you can talk to everyone in Japan. Most Japanese understand the Tokyo dialect, but not all of them can speak it. My son in law from Okinawa went to school in Tokyo just to learn the Tokyo dialect because it is considered more universal than the others. There are big word differences from one dialect to the next in Japan. Here is an example: If you want to say, “I go” in Tokyo dialect, say, “ikimasu.” However, in Ibaraki, they say “igube.” for “I go,” and my Japanese son in law and I think people from Okayama say “ikou” for “I go.” On top of that, the kanji is just flat hard. You will not be able to read all the books just be learning to read hiragana. The Japanese love their kanji, and my Japanese teacher said it would take twelve years of schooling in Japan to learn to read the newspaper in Japanese. This means you can’t take a book home to read and plan on looking up the words you don’t know in the dictionary, but we can do that with English and with other languages too. It makes it hard to become more fluent, if there is a barrier between you and fluency like kanji. The kanji can even be a barrier for the Japanese. Once Japanese man told me that he had moved several times, and every time he moved to another place in Japan, there was a new set of kanji on the signs, and he was lost until he studied the kanji on the signs in the new place.
Sometimes it is according to what your first language is as to which language is easier for you. I learned to speak Romanian very quickly, in six months, because I spoke Spanish first. There are Germans who actually learn English even quicker because the German dialect in their hometown is basically a dialect of English. However, English speakers don’t find German as easy as German speakers find English because German has the masculine and feminine forms like the Latin languages, but there are no clues to whether words are masculine or feminine like there are in Latin languages, you just learn the gender of a word as you learn the German words. The Japanese and Koreans learn one another’s languages pretty easily because the grammar is basically mirrored. The Chinese find Korean easy because Korean has a lot of Chinese mixed into it. The Koreans and Hungarians find one another’s languages easy because the Mongolians conquered Hungary, and that is where they got their language. The Mongolian language and the Korean language in very, very ancient times were the same language. Most languages are related to other languages, and if your languages are related, it makes it easier to learn the other. The people from Bangladesh find Korean easier than others because they also use the same grammar. As far as Russian, Slovakian and Serbian are close to Russian. Some consider the Ukraine to be different from Russian, and some see it as a dialect of Russian.
Spanish and Portuguese are so close that they can understand one another when they speak without having studied the other language at all. The main different between the two is the spelling and a few word choices. You see, it is according to how close two languages are as to how easily someone would learn to speak it. For an English speaker, we would find Latin languages and German easier than any others.
When I taught English as a Second Language in a university in America to students from all over the world, the Koreans had the hardest time, and then the Japanese. The students from other countries found English easier. The gap is huge between English and languages like Korean and Japanese. They have a lot more studying to do than people from other languages. The gap is biggest between Korean and English. Korean even has verb conjugations for when we use punctuation in English. They have so many different words just to mean “is” it would blow your mind! You must know the levels of society to know which verb to use, and not just the conjugations. You conjugate not only verbs, but also adjectives, etc. Korean is extremely different from English, and Japanese has many of the same characteristics as Korean.
I have only ever taught one Russian student, and I never knew enough about Russian to understand her problems. I taught her in Romania, and she couldn’t’ even speak Romanian. I couldn’t speak to her in any language, just teach her English, and it wasn’t easy for her or me, but she began talking to me in English a little before I was finished.
I hope this gives you a better perspective on people trying to learn languages and which one you might find easier. As well as, a perspective of appreciating what the language learners go through to try to learn another language.