How to fix menu issue in OpenCart?

Question

css

Good day

Such is the problem because of the selected class, after opening the menu, it closes immediately, who can tell how to eliminate or how to override the class so that there would be no problems with styles, since I tried to put display: flex in its place; display: inline-block I tried almost everything, but it doesn’t work out, the class still doesn’t disappear, can someone tell me how to make it work so that everything works?