Normally, sale posts from members who have just joined the forum are frowned upon.
It is normally acceptable to post a little information about yourself before making the "for sale" post.

That said, items for sale should go in the "I want to sell" thread

If you need help with prices, if you have the model numbers, you can look at ebay.de or ebay.com and select "completed/sold" items to get an idea what those items have sold for.
You can also check other sites (catawiki.de, tradera.se, etc)

Vänliga hälsningar

Mike C