Progress bars do not display correctly on Firefox

Question

Does anyone know how to fix it?

Answer 1

Without looking at any code, coming up with a "fix" is almost impossible. Please show your code so that others can provide help.

Answer 2

I meant the standard form Sololearn uses to introduce HTML ("Hey! I'm Alex..."). There is a mistake within the CSS, namely:
progress::-moz-progress-bar
I corrected it by replacing -moz- with -mozilla-. Everything works fine now