What computer to buy?

It used to be Toshiba.  But lately the company is making some changes.  I don't know.  Too much insider info. involved.  For my money it is  still Toshiba.  But  you know.

I don't how Walmart Online works with Germany, but I'll give you my results with refurbished HP laptops in the USA - maybe there's a similar deal in Germany.

I had very good performance from the HP refurbished computers that cost around $300 (similarly about 300€) from Walmart Online.  The laptop I'm using right now cost $319 (refurbished: passed back through the assembly line and good as new, but it's $799 new) and was bought in late 2015. It has a 17.3" (43.9 cm) screen, a 3.2 GHz quad-core processor, 8 GB RAM, 1 TB HD, Windows 10, SD Card reader, DVD burner/player, Wifi, nice speakers for a laptop, a full-size real keyboard, a front-facing camera, and all the other usual things but no Bluetooth.

It runs Stockfish 8, through the Lucas Chess Program, at 20-ply at about 70 seconds/move.  For 12-ply its an avg. of 1 second/move.  It runs 1080p Anaglyph 3D movies without a glitch - and most computers, desktop or laptop, can't do that.

Wal Mart went broke in Germany
I usually buy on Amazon but it seems like a lot of outdated computers are being sold for the same price as they used to be back then, for example I saw computers that are 2 or 3 years old (you could see it on the reviews) on amazon and the price staying the same or changing very little, many are not getting updated.

I think the best deals you can get on ebay (maybe used)...but with all these different processors, processor generations, graphic cards I got no clue if I'm getting a deal or being ripped off, seems like you gotta work with computers to be able to compare the different hardware.

I think ebay is a good place. Large corporations will often get rid of old stuff and update, but is still good for home use IMHO.

I have a low end Toshiba that i paid $200 for at wal-mart a couple years ago.  

My HP Pavilion laptop was about $700 new. Nothing fancy but it does the job. I wouldn't get a desktop unless you are going to do some serious gaming or need a souped up pc with extra everything for work or some other reason. I think stationary computers are a little old school, especially considering how powerful laptops are these days. For chess analysis a laptop will more than suffice.