why my villagers stop foraging after i discovered the farm?
i have to keep an eye on them to drag them on the berry bush all the time???

any idea on that? or suggestion?

Well do you have crops on farm? Check villager's like/dislike.Long as villagers is getting foods to food bin I think it isn't a big problem

nope, no crops on farm, that's why i need to forage the berry bush. also checked the like/dislike, farming is checked for both foraging, harvesting, and fishing as well.
so, villagers confused and they won't do what you want them to do.

Part of the challenge is to keep them on task. They always want to move the boulder, do the laundry, curious about the ruins, rock, cactus, or strange patch. Some of the villagers are lazy or stubborn...some are "workaholics" Especially if they are a Master Parent! Whatever task you want them on, just keep dragging them back there till they get it right.

If the crops are growing and not yet ready for hravest, then the farmers will sometimes "water the crops" rather than forage or fish (if you have level 3...) If you are watching the game "live" you need to watch for this and redirect their work efforts either by moving them to the berry bush or ocean, or changing their "preferred" job.

I believe I saw mentioned somewhere that when the game is turned off, the framers won't "water the crops" so sometimes it might just be better not playing during the growing season, or switch to a faster speed if playing at a lower one (or both.)