Please ensure that the .htaccess file is uploaded to your server and is updated to the latest version.
If the file is exists and the issue continue, kindly contact your host provider to enable mod_rewrite on your server.
If you are using a VPS with Ubuntu Linux installed, please follow this guide.
Folder permission error maybe the cause, or apache issue, please inform your host provider and let them fix it for you.
Go to Admin, Site Settings > Max upload size and increase the value, and also contact your host provider and let them increase the upload limit and max_execution_time if the problem persist.
For the main website, You can edit the stylesheet from themes/default/css/main.css and themes/default/css/responsive.css
For the user account dashboard, You can edit from themes/default/layout/account/assets/css/app.min.css
For the admin panel, You can edit from administrator/assets/css/app.min.css
Login to your admin panel
Enter your company bank details and click save to enable the payment for users
You can add or edit adbooster package and price from your admin panel Payments Management/PaymentSettings
After you have bought the SSL certificate.
Open .htaccess file, under "RewriteEngine On", copy and the paste the code below:
RewriteCond %{HTTPS} off
RewriteRule (.*) https://%{HTTP_HOST}%{REQUEST_URI} [R,L]
More information will be provided once the update is available