This question is actually difficult to answer. It depends on your native language. If you grew up native English-speaking, it will seem easier to learn than other languages. If you grew up speaking a different language, you might compare it to other languages you learned. To get a real feel for it; maybe you'd need to do a twin study placed in "identical" homes in places of two different languages, and then have them learn the other's language and see how well each do. Or have someone who speaks English learn another language and then erase their brain, have them start out learning the other language and then have them learn English.
How long does it take to become fluent in a different language? Most people can study the basics of a language, spend two or three years in a country of that language, and speak it almost as indistinguishable from a native speaker. Except English, even if someone has lived in an English-speaking country their entire adult life, you can still identify that they speak English as a second language. Add to this that most native English speakers still barely have a a grasp on it.
English is the most "common" language in the world not because it is "easy", but because only a few hundred years ago there was this empire of English speakers from a little island in Europe who took over half the damn planet and made everyone they subjugated learn it. Much in the same way most European languages are based in Latin, they are called Romantic languages, not because they are sexy (well... yeah, they're also sexy), but because of the Roman empire. English has a lot of Latin in it, as well as pieces of almost every other European and Middle-Eastern language that was around at the time it started coming together.
As for the language itself; here are some thoughts:
Most of the problem comes in vowels. what does "a" sound like? way, car, bat. Doesn't "ie" sound like that sometimes? How about "ie" for that matter?
I before E, except after C, and when sounding like A as in neighbor and weigh, and weird, and their (still an A sound, but a different A sound).
How about weigh? way?
Plurals:
Ox - Oxen
Box - Boxes
Goose - Geese
Moose - Moose
They're their there
To too two
Rhymes:
Tomb Bomb Comb
Naked Baked
Ph, f, th, gh,
Bow: to lower the top half of your person, the front of a ship, an early weapon, or ribbon in a knot?
To the later examples, bough.
Bough/bought/bot/ought
Knot/not
Through thorough rough
Synonyms, just synonyms.
Every language has exceptions. English seems to be built on them.