Can the manufacture access my wallet with the private keys if i encrypt the wallet on bitcoin core?
THEY CAN SPEND MONEY YOU THINK IS IN YOUR WALLET.
This question sounds like a misunderstanding of what a wallet is.
A Bitcoin wallet does not ever contain money.
The only important information in a Bitcoin wallet is a secret number called the "private key".
Anyone who knows this private key has control over money sent to addresses that were created from that private key (including modern hierarchical deterministic HD wallets that contain many private keys derived from one common secret number).
So any changes of passwords or encryption applied to your wallet has no effect whatsoever on the ability of other people to spend your money - if they already know the secret number.
The safest thing to do is to sweep (not import) that secret number (private-key) into a new wallet - this transfers money to the control of a new and different secret number that no one else knows.
Before deleting anything, make backups, test recovering from backups. Write your recovery-phrase or private key down somewhere very very safe - somewhere you can go and get beck if you lose your phone, if your PC is stolen or if your house is burned down.