I would like to buy a good bike worth 400-600 Euro? Only I do not necessarily want to pay a lot for the brand, but rather for the quality. D. H. I do not want an Apple but a Huawei in the bike area, to put it clearly.
27.5 inches, with rear wheel and front suspension. Can also be older models. Brakes do not care.
For this budget, this is not feasible if a good rear shock alone costs 300 euro! Unfortunately I have to take all illusions from you. You will find something like this somewhere on the Internet, but with huge Qualtätbeitschränkungen afflicted, rather Baumarktiveau.
Let's put it this way: an "Apple" in the front and rear suspension of the bike is loose at 4000 euro, a "Huawei" like you are still looking for 2000 euro.
For so little money, you will be lucky enough to find a nice Fully on the used market. Good beginner completions start new depending on the category at 1500-2000 euro.
Huawei would most likely be senders like Canyon, Radon, Rose, YT or Propain. Apple the expensive brands like Pivot, Specialized, Santa Cruz or Intense.
Even on the used market it will be very difficult to find a clever fully in your budget.
And "Brakes do not care" sounds a bit strange for the component on which your health and your life most depends…
What do you have in mind with the wheel in the first place? What are your requirements?
Sports? Everyday life? Forest? Public roads and also in the dark and bad weather?