Trim leaves touching dirt?

That’s DE dust for a big issue I got rid of

You can remove a few top fan leaves. It's okay if they touch dirt. That looks like powdery mildew though. Unless you know it to be something else, mix up a mild solution to kill it. Once it starts budding it's too late.

So I should cut off the bigger leaves? Now or latter? And where should I cut them? Close to the main branch?

Yeah you should and leaves can touch the soil no issue, as long as the soil is not wet for too long while making contact with the leaves because it can create the conditions for fungi.