Translation:Is it difficult to learn Chinese?
Probably depends on your cultural background. I'm finding it incredibly difficult as it's so different from European languages. Even Russian had something I could pin to existing knowledge. And the writing system is very complex - after several months I can just about write the pronouns, and barely read little more. It's certainly a challenge, but fun.
很 is often used for "cadence" or to make the sentence "flow". Note that here we have groups of 2 characters 学习, 汉语, and 难吗; so this flows nicely. Without 吗, as just a statement, 学习汉语难 doesn't flow as nicely so the speaker would more likely add 很. This is by no means a hard and fast rule and there are many exceptions; like 要不要 etc.