Inventory

Based on any documents from that time, should I still enter them as trade goods?

In principle, you are allowed to contribute items that you purchased before you started your business. Of course, you must have a document.

I bought them second-hand several years ago and don't have any documents from them. Can I also enter them as a contribution of 34,000 @ 10,000?

You won't get very far without a document; you need some kind of document.

Can't you just enter it as a contribution at the start if you can prove the price?