Realistically, for that kind of budget, your options are limited to (pretty much) a Ryzen5 2400G IMO.
There is a seller, selling a bundle here:
https://www.amazon.de/dp/B07B25272L/ref=sspa_dk_detail_1?pd_rd_i=B07B24XSD5&pf_rd_m=A3JWKAKR8XB7XF&pf_rd_p=2444543729105426210&pf_rd_r=TJPDBDQWDV8FGPSPC18B&pd_rd_wg=S2Amt&pf_rd_s=desktop-dp-sims&pf_rd_t=40701&pd_rd_w=xZHx3&pf_rd_i=desktop-dp-sims&pd_rd_r=4e34a0c3-9116-11e8-a749-4b358e0caedc&th=1
Typically, B350 boards will need a BIOS update to support the 2400G but, given it's being sold as a bundle, I would assume it has been updated -- although you'd probably want to reach out to the seller(s) to verify.
2400MHz DDR4 is pretty slow for Ryzen though, so I'd suggest manually overclocking that to 2666MHz or greater, if possible.
Unfortunately, that's the vast majority of the budget gone.
Still need a Case, storage and power supply.
A 1TB appears to be ~40EUR
https://www.amazon.de/Seagate-ST1000DM010-Interne-Festplatte-Barracuda/dp/B01LY65EVG/ref=sr_1_4?ie=UTF8&qid=1532638896&sr=8-4&keywords=1tb+hdd
A good quality PSU is another ~40EUR
https://www.amazon.de/XFX-P1-400B-XTFR-PC-Netzteil-Watt-Gold/dp/B01AK9NOLM/ref=sr_1_3?s=computers&ie=UTF8&qid=1532639008&sr=1-3&keywords=xfx
Putting you over budget, without a case.
Luckily, there are some budget offerings there:
https://www.amazon.de/Nox-NXFORTE-NOX-nxforte-Computer-Geh%C3%A4use/dp/B00M40U4NM/ref=sr_1_2?s=computers&ie=UTF8&qid=1532639065&sr=1-2&keywords=computer+case
So the total is roughly 440EUR.
OR, you could do the same configuration, with the Ryzen3 2200G and an B350 motherboard, but there's a sizeable tradeoff in performance by doing so.
https://www.amazon.de/Memory-PC-Aufr%C3%BCst-Kit-GigabitLan-MultimediaKIT/dp/B07B26R8NJ/ref=sr_1_17?s=computers&ie=UTF8&qid=1532639136&sr=1-17&keywords=2200g&th=1
Brings you to around 370EUR