I don’t know if it’s a problem of incompatibility with the theme (olympus) or a plugin but I can’t put an icon. When I click on the button change the icon. Two cases arise: Either it stays on the same page, i.e. the menu page, or it displays barely legible icons with questions sticking to certain icons that I cannot select

Hello sir,

We apologize for the inconvenience, but in order to assist you with your issue, we will need access to your website. Can you please provide us with the login credentials ( in a private reply ) so that we can investigate the issue further?
Your cooperation in this matter is greatly appreciated and we will do our best to resolve the issue as quickly as possible. Please let us know if you have any questions or concerns.

Thanks
Bishal