You can update theme via 2 ways: Via Thim core or via FTP.
1. Update Via Thim Core
Thim Core plugin allows to update theme without resetting your settings and customization. However, you should always backup your files and databases before updating.
Follow these steps below to update Galax theme via Thim Core:
Step 1 – Visit Galax > Dashboard and login with your Envato account.
Step 2 – Click Update now.
2. Update Via Ftp
Follow these steps below to update theme via FTP:
Step 1. Log into your Envato account on themeforest. In your Download page, find Galax theme and choose the Installable WordPress Theme.
Step 2. Login your FTP account via FTP software to access your host web server. Navigate to wp-content/themes folder to backup your current Galax folder if needed. The contents on your site will not be lost but if you have modified the code then the changes will be lost. You have to modify them again after updating.
Step 3. Extract Galax.zip that you downloaded from themeforest
Step 4. Upload new theme folder Galax to wp-content/theme to override the existing files.