Displaying issues on Optimize Press theme

Hello everyone.
I’m having the problem, that the site theme at my site https://bewerbung.teamspirit24.de is having some issues in diplaying the grafics correct.

The footer simply doesn’t show up, though he is shown in the html code.
Also the buttons are beein displayed double.

I am using the Optimize Press (v. 1.57) theme, which recently began to make problems.

All plugins are temporarly deactiveted and the problem continues to exist.

I really appreciate your help guys, thanks in advance!