No problem! If it weren't for that one phrase I would've thought you were a native speaker, your English is very good.

I don't think I've ever heard a native speaker say it, but I could definitely imagine it coming out of a native speaker's mouth with that pregnant pause, specifically. Like an acknowledgment that you're about to say something a bit grammatically awkward.

I only mentioned it because I used to think correcting people's English was rude, until I had a long work engagement with a French guy whose English was pretty good but not quite native. He insisted that I correct his written English if I saw a mistake (i.e. in documentation, proposals, etc.), otherwise he wouldn't learn where it was wrong and how to improve it.

To my ears it “since years” sounds like it’s missing an “ago” after it (or like the GP said “for years” sounds even more natural).

It makes me think of another similar one: I've noticed that British English speakers will say e.g. "the new iPhone will be available from September 20th"

To my ears that sounds like it's missing an “onwards” after it (or “starting September 20th” would sound even more natural).