Desktop PC: SSD with ubuntu doesnt install after installation with my usb

Hi,

good day. I would like to install Linux on my SSD - from my USB stick.
But after the installation it doesn't work with booting from my SSD :(
Maybe someone can help me :confused:
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As far as I can remember I installed an ISO on my stick yesterday:
Program for USB: UNetbootin
ISO: ubuntu-20.04.2.0-desktop-amd64
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Now I have proceeded like this:

• I connected the USB stick and the SSD.
• Then I booted the USB stick.
• I set that in the UEFI.
• Then I moved on to the OEM installation process.
• I chose the last option to create a self-defined partition, because I don't want Linux to be installed on my stick - it should be on the SSD.
• I selected the SSD and deleted a partition ext4 with 240 GB with "/" directory and then one with "/ home" root directory - no idea why
  :scratch:
  also created a 100 MB EFI partition: ???:
• And no matter what I have partitioned so far (about 10 times so far) - Linux never boots - the name always comes from my mainboard and nothing else ... it can of course be that something boots after 10 minutes, but had no opportunity / patience to test that
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I also see in the UEFI that Ubuntu is "on" the SSD.
But it just doesn't boot: shocked:
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I'm looking forward to your suggestions etc
:hattip: