Welcome aboard, Hope you like our products and our support!
When you install the Quickstart file it's by default content language is set to English, so when you wish to create a multi-language website then you need to assign all the menus and modules and almost every other thing for that language.
Talking about images not showing or watermark images are shown that's because those are paid images and we cannot give them away in our quickstarts as free, you need to replace those with your content.
And YES absolutely quickstart is a good option for long term use because here you get a lot more content and extensions that are not there in other files. So you are doing great!
If you like our support and products, tweet us at joomdev and let the world know about it.
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