Metus24 try accessing the /admin page. If you are still logged in, there's a possibility you see the "emergency" version of the page that lets you disable extensions. I'm not sure whether a route definition conflict error still lets you access that version of the admin panel or not.
If you can't open the admin panel and don't have SSH access, then the next step would be to access your database using a tool like phpMyAdmin, select the settings table, then find the line for extensions_enabled and modify the value column which contains a JSON-encoded list of enabled extensions. Remove the extensions you want while making sure the object is still a valid JSON array, or set the value to [] to disable every extension.
If none of this is possible (which would be surprising) the last solution would be to download the entire website via FTP (vendor not necessary), remove the extensions from composer.json, run composer install locally on a different computer, then re-upload everything including the vendor folder to the hosting.
