I can't edit certain parts of 5e sheets

It seems i can't change some stuff on 5e sheets, when i change classes it seems it doesn't apply at all and i can't seem to get attacks and spellcasting rolls in, I think it's my browser that's the problem, and i'm on mac 10.7.5

Since we can't see what browser you're using... what browser *are* you using?  Keep in mind, Roll20 only supports Firefox and Chrome.  Nothing else .

Ah my bad, it's chrome version    49.0.2623.112  and roll20 doesn't seem to work on firefox

Roll20 *does* normally work on firefox.  I haven't used Mac's since 1995, but a brief googling tells me that chrome is up to the 80s in major version number.  When is the last time you updated chrome? :)  That said... Minimum number of steps to reproduce the problem Description of setup Browser + Version Browser Addons/Extensions Operating System Bug Triage Results Please carefully work through to the first three steps of our guide to Solving Technical Issues : Step 1: Make sure to use the right browser Please check if these issues persist when using both Chrome and Firefox. Step 2: Ensure that there are no extensions/addons interfering with Roll20 Please disable all add-ons/extensions. Step 3: Clear your cache If none of the above succeed in resolving the problem, please thoroughly work through Step 4 . (Don't forget the complete Console Log!)