FYI coinhive has 30% fee, you'll get 30% more coins mining monero on a real pool, along with a more optimized cpu miner than a javascript wasm one. Coinhive only makes sense for sites with a huge userbase that spend a lot of time on the site that prefer not to have ads, like mining to pay for premium access.
30% is too much

Do you have some tips / a guide for monero cpu miner?
Agreed, too high. There is a post about Monero just use the search function