WP deletes automatically our website when updating

Hello, WordPress automatically deletes our website based on premium theme or it significantly damages the home page when updates to new WP versions. After a few such problems, we had to backup our website, but finally discovered the cause. Namely at WordPress theme directory there is another theme with the same name from other company/theme supplier. So when WP updates, it reads/update the free version of this other theme, and automatically install it on our website, and at the same time it causes complete deletion or damage to our site. A notice for an update of a new version of this theme appears on our site. The image of this notice is from our website theme, but the version update actually refers to that other theme with the same name. If we click to update, WP install free version of that theme instead of our website theme. This is unbelievable! How can we solve this problem, because WP deletes our website when updating, and install automatically other free theme with the same name. Thank you.