Fóram Tacaíochta Firefox

Hi I'm developer and i develop a site and when i QA it all are good in other browsers expect Firefox,some colors are different in Firefox,images are not displaying, in text fields there are little arrow icons, widths & heights sucks in some content why the hell is that i think Firefox is suck now i have to wast time to write other CSS file when some one comes with Firefox that need to change content.

I have a problem with this website: https://togamas.com/

The search result in this website is not properly displayed by Firefox, either PC or mobile android. I tried using Edge in PC and Chrome in android, and the search result is shown. I don't know why the problem only appear in Firefox.

I put screenshot images of the problem. The one at the top is Firefox, while the bottom one is Edge. The search query is the same, but Firefox doesn't display anything.

Any help?

As per included image, dropdown prompt fonts are too small to read. I've already tried the devp font change, but that doesn't do anything to the font size here, and I don't see any font setting regarding dropdown prompts in settings tab.