Max amount of posts a day?

There isn't really a magic number. I'd rather post 1–2 good pieces of content than 5 average ones. Consistency matters much more than volume, and posting too much can actually reduce engagement if your audience starts skipping your content.

I did like 5-10 posts per day but Instagram hardly pushed ne accounts now days.

For fresh accounts not recommended more than 5-10 per day.

Quality matters more than quantity.
I'd ask instead: How many quality posts can you consistently publish every day without hurting engagement? That's usually the better metric.