I struggle with much more than just concentration. It helps me indeed if i'm interested in the subject but it's not that simple.

Pomodoro is cool. There are many apps in Google play. My favourite is pomodoro challenge. Also try raise the bar app.

Since yesterday i'm trying Marvel piano premium and it's cool as It seems to put my brain on the right track.

Unfortunately there is nothing better for concentration as to turn off your comp for at least two weeks and be diligent in your concentration training. Instant culture isn't always the solution