"Watashi wa nihongo wo benkyou shimasu" does not mean "I'm learning Japanese" First thing first. They say "します" is called present form "現在形". But "します" HARDLY describes the present action going on now.Instead "します" usually describes future action. For example. 今 いきます(ikimasu) : I will go very soon (not yet going) 今度、やります(yarimasu): Next time I will do. (not doing now) 私はアメリカにいきます(ikimasu)：I will go to the USA (not going now) Lots of Japanese learners write "私は日本語を勉強します" in their ITALKI profile. Probalgy they mean "I study/am learning Japanese", however "私は日本語を勉強します"does not mean that. Instead it means "I will learn Japanese (Now I don't)". e.g, "私は来年、日本語を勉強します". The right words are "私は日本語を勉強しています(shiteimasu)" , which means "I study/am learning Japanese" FYI: Japanese verbs have no system of tense, thought it appears to have it. It has only system of aspect, "do/done" FYI2: I think the similar thing happens in English. "What do you do?" does not mean "What are you doing?" but "What's your work?" "What do you drink?" does not mean "What are you drinking?" but "What's your favorite liquor?" Verb in present tense often describes not ongoing action, but who you are, or profession. In my opinion, the term "present tense" is a source of confusion.

Generally speaking, 私は日本語の勉強をします（Watashi wa nihongo wo benkyou shimasu.) means "I learn Japanese" or "I'm going to(or I will) learn Japanese". On the other hand, 私は日本語の勉強をしています（Watashi wa nihongo wo benkyou shiteimasu.) means "I learn Japanese", "I'm learning Japanese", or "I've learned Japanese". However, there are some exceptions. We usually use these two terms depending on contexts. If you tell me your preceding/following sentences, I'll teach you which word is better.