What about the button being cropped?

Add the Following CSS code in "Custom CSS code" textarea, it should solve the issue. 

#wpforo #wpforo-wrap .wpforo-profile-wrap .wpfpm-message-div {
   right: 6% !important;
}

I see another CSS conflict with the active theme or other plugins related to avatar size (see screenshot). It's a little smaller than it should be. To solve the issue just add the following CSS code in "Custom CSS code" textarea as well and check again:

#wpforo #wpforo-wrap .wpforo-profile-wrap .h-picture .avatar{
   width: 100% !important;
}

Please don't forget to delete all caches before checking.

What about the button being cropped?

https://mitzpe-ramon.com/forums/

All wpForo phrases are located in Dashboard > Forums > Phrases admin page. Just find the phrase and translate it to your language.

If you can’t find some phrase you can either add it using button or navigate to Dashboard > Forums > Dashboard admin page, click on "Rebuild Phrases" button and try to find the phrase again. 

Please don’t forget to delete phrase cache in Dashboard > Forums > Dashboard admin page.

More info here: https://wpforo.com/docs/root/translation/quick-translation-phrases/

I use the Private Messages addon.

Translated to Hebrew most of it, but can't make the main "Send a Message" button show my translation.

Another thing is that the button is not located well, and is going out of the page (screenshot).

Thanks