I have a lot of difficulty when it comes to focusing on my learning. The moment I try to concentrate, all kinds of thoughts enter my mind and confuse me. This especially happens when I learn Gemara. When I learn mussar or halachah, though, this doesn’t happen as much.
Spend some time on learning Gemara, and give it your best. The rest of your times can spent on learning halachah and mussar. Gradually, and with a lot of patience, you should increase the amount of time you spend on learning Gemara, to the best of your ability.