How can I use my laptop with the 2nd screen when my laptop is closed?

Can I adjust somewhere that my laptop is closed, but still runs on the 2nd Screen? Have seen that in a few videos haha. Ps: have a windows laptop

You can specify in the system settings what should happen when closing. If you set it to "do nothing", the laptop will continue to show the desktop on the second screen after closing.

Which windows? Energy options are the problem. You can continue to use your monitor if the laptop does not go to standby when the screen is closed.
If it continues to run, the external monitor is also in operation.

But have win10

Then the window for the settings looks different.
Here is a description of where you can find these settings in the different Windows versions, also for Win10.
https://www.pctipp.ch/tipps-tricks/kummerkasten/windows-10/artikel/notebook-beim-zuklappen-nicht-ausschalten-50049/

Themselves to blame.