How do I switch between graphics cards?

I have the following problem; After my actually more or less suitable for gaming laptop by viruses and too much waste gradually became slower, I decided to set it up again. That worked well for now. Of course, my laptop (Lenovo) has two graphics cards. Once there would be the Intel (R) HD Graphics 4600 and then the NVIDIA GeForce GTX 960M, which I would like to use for games. Now I have the problem that the laptop always uses the Intel and I see no way to change it.
Here's what I've already tried:

1.

I deactivated the Intel graphics card in the Device Manager, but that only made my second connected screen black and unusable, the laptop told me that instead of using the Nvidia, it had a screen now probably operates without graphics card. (However that works.)

Second

Then I right-click on the desktop (Windows 10) called the NVIDIA control panel. Under the Manage 3D settings tab, I was able to choose what I would like to set as the preferred graphics processor, the integrated graphics or the NVIDIA high performance processor. However, after selecting the Nvidia, there was no difference anywhere.
Under the next PhysX Configuration tab, I was again able to select the Nvidia as a PhysX processor, but both of my monitors were still running as Intel, so I could not change that, which brings us to point 3.

Third

Right-click on the desktop again, display settings, advanced display settings. Here were my two screens listed, again both connected to Intel (R) HD Graphics 4600, which could not be changed.

4th

Finally, by pressing on F2 during bootup in the BIOS penetrated, here it was a bit complicated for me as a clueless. Under Configuration, I switched from Switchable Graphics to UMA Graphics at Graphic Device, which meant that the Nvidia was no longer listed after booting. Then back to the BIOS, switched back to switchable graphics, enabled NVIDIA GPS and disabled Intel Virtual Technology, but that, as far as I know, made no difference.

That's all I think I've tried so far, I hope someone can help me.

This is Nvidia Optimus… On the desktop / in 2D applications, only the internal graphics card is used, in 3D applications then the dedicated card.

The behavior is completely correct.

For the possibility of switching between Intel HD and Nvidia Geforce, the functional extension "Nvidia Optimus" must be installed.

Lenovo offers these special Optimus graphics drivers for various notebooks in its range. Here is an example - link to Lenovo (for your notebook model you will have to look for it separately):

https://support.lenovo.com/...s/ds502391" class="text-primary">https://support.lenovo.com/...s/ds502391

general:

https://support.lenovo.com/ma/de/downloads/ds502391

Unfortunately, you have not communicated the exact type designation, so only hints and conjectures:

Various reasons for your problem:

A graphics card is disabled in the BIOS. You have checked, there's a corresponding entry, but not the desired reaction.

Probably wrong or not all chipset drivers have been installed. As a result, your system did not recognize the hardware correctly.

It could also be that the Nvidia graphics card is simply broken. Then of course you can test a lot, but without result.

Here is an identical problem and a very good procedure is described to narrow down the error:

https://forums.lenovo.com/...-p/3602229

Suitable for your notebook or a similar device:

https://forums.lenovo.com/...-p/3868550

If you install drivers, please only use those offered by Lenovo, the drivers of Nvidia do not necessarily work.

And another report: https://forums.lenovo.com/...-p/3273016

Lenovo forums and the original drivers that Lenovo offers should solve your problem.

If that does not help you, you're welcome to contact me.