わたしはえいごをべんきょうします。(When I hear this sentence without any context, what I imagine is "I'll study English".) わたしはえいごをべんきょうしています。(It means "I'm studying English now" and "I study English habitually", "I'm in the situation that I study English / I already started studying English".) With more context: わたしはあしたがっこうへいきます。(I'll go to school tomorrow.) わたしはまいにちがっこうへいきます。(I go to school everyday / I'll go to school everyday.) わたしはまいにちがっこうへいっています。(I go to school everyday.) わたしはバスでがっこうへいきます。(I go to school by bus / I'll go to school by bus.) わたしはバスでがっこうへいっています。(I go to school by bus.) If you need more examples, please let me know. I hope this was helpful.