Theme override for 3rd party integration

Site URL: https://www.highridecycle.com/slo-schedule-copy

I am in the process of integrating a new booking system into my website (boutique cycling studio). All integrations are working properly, but I'm having trouble overriding the themes of the integration to match the rest of my website.

I have added a theme override to the Custom CSS section (and it displays properly in the preview section); however, when I save changes and refresh the page, it refers back to stylesheet of the integration (which I placed as a code injection in the header). It seems to me, the problem lies in the order in which the customizations are appearing on my pages. 

Looking for a solution that would enable my Custom CSS to override the integration stylesheet I injected in the header (without switching to developer mode)?

try add !important to after

eg: font-size: 10px !important;

12 hours ago, tuanphan said:

try add !important to after

eg: font-size: 10px !important;

This worked! Thank you SO MUCH!