I believe you are undoubtedly the victim of a scam.
It is extremely unlikely you will be able to trace the money to any identifiable individual. Bitcoin is designed to make this very difficult.
I suggest you firstly report to police that you are the victim of a fraud, secondly accept that the money is irretrievably lost and move on with your life.
in the form of them giving me the key for getting access to the wallet.
Something I associate with scams.
If this is an online wallet (custodial) this sort of thing is normally explicitly forbidden in the terms and conditions. And for good reasons.
If it is a more normal wallet, it is an idiotic way of donating money. That by itself is suspicious.
Is it ...
How can Bitcoin transactions be traced if you can change your address?
In Bitcoin you don't change your address. You create new receiving addresses.
This is normally done so that a new address is created for each new transaction with the intention to increase privacy.
However in each transaction there are inputs and outputs and if a transaction has one ...
Chain analysis companies use many heuristics to link addresses into wallets.
The most popular being:
common input heuristic where all addresses are grouped by the premise of being inputs to the same transaction
change analysis heuristic which looks at the transaction outputs trying to group them by recipient and change address
other methods, like grouping ...