Hello,
how should I repair the GRUB?
After resizing the boot sda2, the screen stay black with"GRUB" on the top left and the PC dont boot.
No reaction anymore from the keyboard.
All grub config files etc. are there (I checked this with a knoppix7.2 USB).
Thanks for any advice.

Check to make sure the uuid of the partition is the same as that shown in the grub.cfg.

blkid as root should run the uuid for each device.

Also use the livecd of any pre-antiX-15 and/or MEPIS to fix a broken grub. It needs to use fix grub-legacy

THANKS!
I was trzing a lot the whole daz.
I am now installing antix15 in the same place of antix13 and making the required settings .. kezboard etc *it boots again..
I will have a look at mz old antix13 installation setup here and will be probably successfull.
Topic closed.

@ floppy -- I have done the same in the past, make changes and resize a partition, and forget about the uuid. All that was needed was to 'update grub' BEFORE I left that partition. Sometimes it takes a 'boot to the head" to realize what I did or forgot.