After Richard's corrections, you have a good sentence but there is still room for stylistic improvement. Your sentence is really composed of three complete sentences glued together by two conjunctions: 1. "This topic is not interesting" 2. "I have to study it anyway" 3. "I have to be able to ..." It ends up feeling more like a paragraph than a sentence because none of the three sentences dominates the others. A sentence needs to have a purpose. To fix this, decide which sentence is the one you want to emphasize (I'll use #2). Then turn the other two into subordinate phrases: "Finding this topic uninteresting, I must nonetheless study it to be able to speak on a variety of topics." In this construction, sentence #1 has been turned into an adjective phrase, sentence #3 has been turned into an adverbial phrase ("to be able..."), and #2 is now the single main clause. Try to do this most of the time: for each sentence pick one main subject and verb. Then embellish them with subordinate clauses. Make each sentence say something specific.

This topic is not interesting for me, but I have to study it anyway because I have to be able to speak (in) ON different (topic) topicS. Notice that a comma is required after the word "me" because the coordinating conjunction "but" starts a new clause (sentence).