max amount of posts on home?

Is there a maximum amount of posts that can be shown on the home page?
On the home of our website we are showing a (manual) selection of thumbnails from posts to give an overview of our portfolio.
At the moment it is showing 50 thumbs.
We woud like to show more, but when I add ann extra ID of a post it won’t show it, unless I remove an other.

this is the site:
https://www.omniafausta.com

It uses a custom theme I made, started from Tweaker3 and tweaked quite a lot.
I am not sure if what causes the max amount of thumbs is something in the functions of the theme or something in the settings of WordPress itself.

I hope someone can help me, let me know if you need any more info or code.

Thanks!