I don’t know what happened when anki synced it was updated and a lot of cards were removed thousands of personalized cards and it was apparent that in some decks - subdecks wee double I can provide screenshot ! please this is crucial I spent more than 4-5 months personalizing every card
Hello,
You can restore from a backup and get all the cards back.
To do this, follow this tutorial: How to Restore From Backup
This most likely happened because you did not protect your cards, you need to protect the changes you make otherwise they will be overwritten by AnkiHub when syncing.
This guide will have everything you need to know about protecting fields and tags: 🔐 Protecting Fields and Tags
How is this a problem of unprotected tags there is duplicates of decks that appeared out of nowhere + The cards i add i either add a cloze on a original already made card or i add an entirely new card with the tag of the subdeck : which one is probably lost ? the first or the 2nd
If you don’t protect cards that were originally made, for example you add a cloze to an AnKing card, then it will be overwritten
Cards you create from scratch cannot be altered by AnkiHub. AnkiHub can only alter cards that have an AnkiHub ID (for example, cards from the AnKing Step Deck)
Did you recieve any prompt to upload to ankiweb or download from ankiweb like this or no?
No no i was on it. Exemple: I was checking hematology it was around 3000 cards after like 30 mins I came back and saw it became 2200 + the duplicate things + when I was closing anki 12000 notes update downloaded and idk what else
We just pushed out an update that fixed the BNB tags. Were you checking the BNB hematology tag?
I was viewing the hematology subdeck in BNB yes so it was around 3000 cards now its around 2257
Yes this is correct and intended!
But i was studying those 3000 cards entirely now I lost 800 that means ? 
Sorry if i am bothering but i am very anxious and stressed
No, those cards were not deleted. They are still in the deck.
Basically to summarize, around a week ago we pushed a update to the BNB tags which caused the tags in the step 1 bnb tag to go from around 21k to 29k.
Many users did not like this, understandably, since it made it really hard to get through videos without having to unlock a ton of tags, some which weren’t super relevant to the video
So today, around an hour ago, we pushed an update that fixed this. Now the tags are at a healthy normal amount. So the cards are still there, for example you can still find them tagged to First Aid or Pathoma. Nothing was deleted in terms of cards.
No it’s okay, we’re here to help! 
So basically 0 cards were deleted and if i study cards from BnB, Pathoma and First aid about a very specific subject X, I’ll find the same number of cards on very specific subject X that there were 1-2 months ago right ? @Ahmed7
And a small problem that I guess the new update used different tags cause now in some sub-decks I have for example in cell bio:
Sub-deck: Cellular (contains the cards I created myself)
Sub-deck: Cellular_Biology (contains cards created by you anking)
samegoes to a lot of subdecks that you used a new tag in the update some didn’t create a duplicate because the tag was the same i guess @Ahmed7
Correct that 0 cards were deleted.
If you click on a given tag (say for one specific BnB video), there may not be the same number of cards tagged for that specific thing, though the overall number of cards in the deck has not changed nor the total number of cards for the topic as a whole (say, cardio).
Tag changes shouldn’t affect the number of cards in a given subdeck, as card location is not impacted by the tag alterations that went through.
This may be different if you are using custom-filtered decks, though for regular decks (and subdecks) the tag changes won’t affect your existing card counts.
Please let me know if that answers your question, and if there’s anything else I can help with. 