My first grow. Need your advices for flushing and harvest, when it will be. Now is the 68 day

2-3 weeks more to go at least.

Flushing is not necessary (this has been disproven by several studies). THC peak is when all the trichomes are milky. However, it's not always desirable, as the effect is primarily influenced by terpenes and also other cannabinoids, which peak at 40-60% amber trichomes, so you need to experiment a bit. I would always let them go for 2 weeks longer than you think when the right harvest time has come. Before harvesting, 48 hours of darkness to draw out the carbohydrates from the buds, thus getting a better taste later and significantly reducing the chlorophyll content. I can recommend dry trimming, but before hanging, make sure to remove all sun leaves. After cutting, you can place them in osmosis water with phosphoric acid to give the plant the chance to finish its metabolic processes without simultaneously providing carbohydrates and other nutrients, so it has to use the chlorophyll from its cells to maintain these processes.