CSS problem in Top Menu

From Inspect Element Window I can tell my topmenu css is font-size:14px!important;

I’ve tried overriding it by adding another line saying font-size:18px!important; but nothing happens.

From Inspect Element Window I also found out which page the css page is coming from, a folder called font. When I tried editing the page it looked something like this:

“óÏKkÓmº&Nî¼îŒvî¼eÁáÔÚ«T0<˜V BS *
YXžF‚Hªª4ž°ÄDûª¢[®þËFkóXVR•àáõ³GW®tâÎñ¾òî™µõœcèÐäéÉ}{oQJÌZWc¦\åÚ.O|÷ȱ7šòÔ+­+Ü»aïýWMïéH=KtHï¥_Y¢Ö‡@>·£ÛQ™ÇR’ öI “

Did anybody had a similar problem? Please let me know.

Thanks

https://ww.wp.xz.cn/plugins/css/