I am very new at this, but I couldn'd find an answer.

 

I am trying to make my first custom song, and the song I chose has increased speed on the solo part. How do i change BPM only for that part ?

You can anchor the beat where the solo starts by clicking on it (the -->) and pressing the A key. EOF will place a red arrow beneath the beat to reflect this change. Then you can click and drag beat markers that occur in the solo, and the one you anchored will stay put. Alternatively, you can manually set the tempo on the beat marker at the beginning of the solo and that beat won't go anywhere.

Thank you very much  :)