How Can I speed up decrypting? I have a recovery company retrieving my scammed bitcoins. They have moved them directly to my brand new wallet but the decryption process is very very slow. They say I should purchase more bitcoins and deposit them in my wallet to create history. Will that speed up the process?
You are likely being scammed again.

The vast majority of bitcoin recovery companies are scams. The ONLY scenarios in which coins are recoverable are if you mistakenly sent them to another address in your wallet (such as an address after the gap limit, sent BTC to an LTC address, ETH to an ETC address, and so on), or if your wallet had a catastrophic derivation issue that resulted in it giving you non-standard addresses which normal wallet software cannot find.

Pretty much anyone else claiming to be able to recover coins that were stolen in scams, hacked from exchange accounts, sent to scammy brokers/investment/mining operations, etc. is also a scammer, trying to capitalize on your loss to extract more funds from you.

Cut your losses now, and do not give these people any more funds.