Semi Tarrasch

I want to learn the Semi Tarrasch but I can't find enough material on it to feel comfortable playing it.

Does anyone know what to do?

This might help. Perhaps it would be a good idea to find some master games in the variation, download pgns and analyze them yourself. Find some ideas, perhaps some repeating tactical shots etc. It might be a good way to learn to play specific opening better.

Thank you again, but all I could find is this, a chessbase course by Mihail Marin and 2 books.

How can that be all there is?

Well, sorry I can't help any further. Perhaps someone more knowledgeable than me will be able to offer you something more concrete.

There is more information here https://www.chess.com/forum/view/chess-openings/semi-tarrascj

but how much do you really need when starting out in this opening? You have the direct Grunfeld pawn structure with e4, were can look at Kramnik games with Nd7, and how to deal with d5 break, and use queen-side pawn majority. Against e3, have Marin approach of going into Queens-Indian approach of NXN, then b6, there is the classic IQP approach covered in one of the books in link, and the modern in the chess stars book with pxp, NxN then Qc7. Marin's chessbase course is 6 or 7 hrs long, and covers english move orders as well trying to be universal.

For a straightforward opening there is more than enough to be starting off with.

 I'll try getting advice from a titled player, thank you for your help.