If you does not see changes that you made on your site or see old version you need to clear your cache. This is possible that you have cache in several places, and you need to clear it everywhere.
If you update theme and see that new features styles does not looks correctly - you have old theme version CSS styles cache and need to clear caches everywhere too.
Clear browser cache on your computer
Check this article for help how to do this.
Clear server cache on your hosting
Some hosting's have built in cache feature, usually its located in hosting CPanel (control panel) and may have some name like "Perfomance", "Site speed", "Caching", "Cache", etc. If you are not sure if your hosting have this feature or can't find it you need to contact your hosting support for help.
Clear WordPress cache on your site
Some hosting's have built in WordPress cache feature, you should see some button in top WordPress menu after login that allow you to clear this, for example "Clear cache", "Purge cache", "Delete cache". Use this element to clear cache.
If you use WordPress cache plugins (for ex. W3TotalCache) you need to clear your cache using this plugins options. Check your plugin documentation how to do this.
Clear CDN cache
If you use third party services for static files caching (for example CloudFlare service) you need to clear/flush cache in this services as well. Refer to your service documentation how to do this correctly. In CloudFlare you can do this in Caching > Purge Everything.
If nothing works for you
If you still does not see some changes on site, this means your hosting may have static files cache feature, that may not have option to manually clear on some servers (like WPEngine). You need to wait some time for cache expiration, after this cache will be updated automatically.
If you can't save any theme control panel options (for ex. colors, fonts) check this article for help:
If nothing help you need to contact your hosting provider support for help.