HTTP Error when uploading pictures and problem with the size of images

For fixing HTTP error, follow these steps:

1. Open the cPanel.
2. Go to File Manager.
3. Search for wp-content.
4. Find uploads folder. Right-click on it and choose Change
   Permissions.
5. A pop up will appear. Set the permission to 755.
6. Finally, click on the Change Permissions button. You will find
   that the HTTP error has gone.

You can find more information about these steps right here.

Regarding too big images issue, add these CSS codes in the Custom CSS Box provided through the Customizer Options:

.woocommerce #primary .images img {
    width: auto;
}