I have CSS Issues + PDF Export not working

Hello there,
i was forced to change my Theme because of incompatibility of many functions. I use now a light Theme well coded and with 70% less plugins. I am now working on the product builder, and i have some issues.

It seems that the new theme is more compatible as the old theme i used before. BUT i have few issues and i hope you can help to fix those CSS.

Information about my theme: There is a Night/Day Mode where you can switch. The Switcher is located on the Top Right side as Sun/Moon Icon which you can click.

1) When you switch to night mode, the Page where the Product Builder Shortcode is placed, it shows everything white, your plugin seems to have a conflict there. https://ibb.co/kHmCDPL And Night Mode https://ibb.co/42jVm7t You can open other pages and see how it looks when Day/Night Mode.

2) I Use Product Builder Ajax Theme, when i open the popup where i can select the product, there is an issue with the background.. Image: https://ibb.co/5rhvZD5 you can test it in my website open the pupup and then scroll up and down.

3) I tried to export the selected products, i can see the file is downloaded, but i cant open it. Its not PDF, its a empty file (not .PDF). The file name is 896f117c-da4a-4cb4-aef2-7391e16a1f6a and if i rename the file with .pdf then i can open the file in pdf and it works. I have no idea why. https://ibb.co/4gtnk41 and then i can rename it in pdf and it works https://ibb.co/mG55HJC

Thats all, i am happy there are not more issues, 2 Issues with CSS and 1 Issue with PDF Exporter.
If you need Admin Access, just tell me, i will send it immediately.

My domain URL, i will send it private.