PC Master Race

CPU 3600, Mobo b450m, GPU 6700(xt), RAM 16Gb 3200mhz

Something like this: https://de.pcpartpicker.com/list/WC2VTY

Comes out at 637€. A little over budget, but that's also all new parts. It's definitely enough for 1080p, often 1440p even.

To get the most out of the budget, I'd definitely be looking at the used market.

Definitely used 3600 for CPU. They go for very little and will pair nicely even with 3070 class cards.

Used 6700 or 6700xt for GPU, but since they aren't as robust as CPUs, do pay closer attention to damages, dust, performance compared to benchmark, and etc.

Used case, because they don't matter unless for looks. Just make sure it allows for air to pass through.

Heatsink can sometimes come together with CPU. I'd be spending no more than 20$ to cool this one. (However, PA120 is kinda too good to pass on, despite being overkill for the CPU).

RAM may as well be new, they aren't very expensive. SP Xpower Turbine, Ripjaws, or Kingston Fury 2x8Gb 3200 or 3600 are all good options.

Motherboard, wouldn't buy used. And I wouldn't be buying the lowest chipset either. b550m DS3H would be reasonable here or b450m ("m" means mATX, which are smaller than non-m, and usually cheaper), depending on if you need the extra features of b550 chipset.

Power Supply should never be bought used, look up tier lists, and go with middle range one for reliability. 550W and over should be enough for the build. Try not to cheap out on these.

Storage, also never to be bought used. Look for M.2 NVMes. SN770 is best bang for the buck imo, but even Kingston NV2 will do fine. 256Gb is enough for OS and some additional software. Imo, that's too little. Get at least 500Gb. Ideally, 1Tb. Mind you, you could always add more later.