How can I restore the MAX32620FTHR bootloader (when erased accidently) ?

Answer:
The MAX32620FTHR board comes with a pre-deployed boot-loader such as you can program your target application to the FTHR board directly without using the MAXDAP interface out of your IDE.
If you accidentally erase the boot-loader you can restore it using the MAXDAP interface connected to a sw-JTAG programmer like the MAX32625PICO-board.
The bootloader-file you have to flash into the target is attached.