Upgrading from Mountain Lion
I cleaned off my computer for our kids and it took off all of the upgrades. When i try to upgrade it the websites either don't open at all or are messed up.
MacBook Pro 15″, macOS 10.15
What is the exact model of your Mac? You can get this information by clicking the Apple menu and selecting "About This Mac". I believe your Mac should be able to upgrade to at least macOS 10.11 El Capitan, but even this OS is too old. Depending on the exact model of your Mac, it may be possible to upgrade to an even more recent version of macOS which may allow you to access websites. However, most browsers today will only support the three most recent versions of macOS which is currently Sonoma, Ventura, and Monterey (the browsers just implemented this change recently). There still may be some browsers with Long Term Support editions which may still be supported for some older versions of macOS, but not for much longer. Sometimes the community will also backport changes into older versions of a browser by forking it in order to get access to websites on older unsupported systems.