Wordpress Logging IN is no longer possible

[rajkrupametal]

Hello everyone, I have a huge problem, I built a WordPress page for my website Rajkrupa Metal Industries in a subfolder because an old Joomla version is running on the server. I then wanted to follow instructions to set WordPress so that it is in the subfolder but started from the main domain. No idea whether the error happened there, in any case, I got an email from WordPress with this message:
A plugin probably also causes problems, WordPress sent me this message:
Error details
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An error of type E_COMPILE_ERROR was found in line 25 of the file / mnt / web219 / d3 / 27/52563627 / htdocs / wordpress / wp-content / plugins / boostify-header-footer-builder / boostify-header-footer-builder .php caused. Error message: require_once (): Failed opening required '/ mnt / web219 / d3 / 27/52563627 / htdocs / wordpress / wp-content / plugins / boostify-header-footer-builder / vendor / appsero / client / src / Client. php '(include_path =' .: / opt / RZphp56 / includes')

And now I can no longer log in, I end up in a redirect loop and desperate.

I made a previous backup via Filezilla, but even if I upload it again, it does not work and I can also access the database. I also backed up the database again in WordPress using the updraft plugin.

Does somebody have any idea?