Hi,
How can a minimize seeding torrents while downloading? there was an option to "stop seeding" before, but now I can' find it. I can stop seeding after download is completed only. Seeding decreases my download speed significantly. That's why a need to disable it while downloading.

You can use medium traffic mode for that case. Go to Settings | Traffic limits and lower upload speed for medium mode, then switch FDM to medium mode.