As in the question, I'm looking for a laptop up to 400 euro. It should be able to run several programs at the same time without being particularly slow. Of course, Netflix and other streaming services should run smoothly.
Take a look on eBay for devices like the Lenovo Thinkpac t440, t450, etc. Or the t540, t550, etc. These are good devices that you can get used cheaply and still use flawlessly today. The devices should start at around 200-300 euro and also offer things like two batteries (one permanently installed, one to change), in order to achieve a long battery life of up to 15 hours, for example.
I would also recommend at least 8 or 16GB Ram and an SSD, then you are definitely on the safe side.
Better a used one with the budget.
For 400 euro there's Pentium and Celeron and the only thing that causes them is aggression.
You can get used HP ProBook / Elitebook or ThinkPad from Lenovo. These are notebooks from the upper class that hold up extremely well.
If it's a new device, I would recommend the HP 15s-eq1305ng (https://www.mediamarkt.de/de/product/_hp-15s-eq1305ng-2709852.html?_knopii=1&utm_id=subpartner-clickid which has enough power with a Ryzen 3 and even a USB C 3.2 connection, which is very rare in this price range. 8GB DDR4 RAM and 256GB SSD hard drive is more than enough. But I can also highly recommend that you take a look around the used and refurbished market.
I would definitely pay attention to 3 things:
At least 8G RAM
SSD should be installed
Windows 10
Personally, I would take this one for under 400 euro:
I can recommend the Acer Chromebook https://www.notebooksbilliger.de/...9vy+678544 or https://www.notebooksbilliger.de/...297+642583, for example, which should be completely sufficient for your purposes.
