Is it safe to resize partitions (with gparted live) after successfull instalation dualboot w7-mint? I swapped partition size by mistake so I need to reduce win partition and enlarge mint part.
There's always a risk when dealing with partition tables or when resizing filesystems. It will work fine nine times out of ten (maybe more than that), but occasionally you'll have a power failure, run into a bug, experience an I/O problem, or run into something else that will cause data corruption. If that happens, you'll have to re-install. Such problems will not damage your hardware (although they can be caused by failing hardware), so if you have no vital data and are prepared to re-install, such a problem will be a time sink, not a devastating loss.
Note that the partition whose start point you move will be at greater risk than the one whose end point you move. This is because filesystem data structures are defined relative to the start of the filesystem, so when you move that start point, the software must recompute a lot more data and/or move most of the data in the filesystem. This is time consuming and increases the risk, compared to simply tweaking a few data structures to adjust the end point of the partition.
One more point: Moving the start point of a Windows partition with GParted on a BIOS-based installation is likely to render Windows unbootable. This isn't the case if you've got an EFI-based installation, though. Windows' own partitioning tool seems to be able to make the necessary adjustments, too. In any event, if you must resize a Windows partition, it's probably best to do that part of the job using Windows rather than using a Linux tool.
Check this out: Change Partition Size in Windows 7 without Losing Data
I think this may be of some use to you but I would recommend backing up your data on both partitions regardless.