>By the way: I didn't change the file. When I compare the file with the active version or any version from local history (ContextMenu>Compare with>...), I cannot detect any differences.
If you compared the version from the HANA Studio and they are the same, then just use the Revert option or do a Check Out of the project. This should overwrite the local version with the version from the server and remove any conflicts. If it were a true conflict you could use the merge tools within the HANA Studio. The message you receive about the REGI merge tool is not actually correct. This is message comes through because HANA Studio calls REGI behind the scenes and just passes back any error messages produced by REGI. There shouldn't actually be a reason to use REGI directly.