Thank you guys for the replies, you said ThemeForest is a good place to buy Milk theme. Are there more known websites to purchase themes?
About modern: there are forums that are easier to navigate when viewing in Mobile devices. Therefore I mean modern, not only the looks of it. Example are LinusTechTips forum: https://linustechtips.com/main/
and Tom's Hardware: https://forums.tomshardware.com/
Also about modern: the forums that I mentioned above don't use tags for everything, they're more user friendly, so for example when I want a bold text it makes it bold in the text editor without
tags, same for urls, images.. and so on, they're more like Microsoft Word editing style (live editing), they also have auto draft saving. Can I have these features on phpBB as well?