The pattern to recognise
A listing that is cheaper than it should be, an owner who is always travelling, and a request for a token amount to “hold” the flat. Any one of these is a reason to slow down; all three together is the usual shape of the scam.
Check the person
Ask who you are dealing with and ask them to verify. A real-person check with matched photos shows there is an actual, identifiable person behind the messages. You can send that request by link, and they do not need an account to answer.
Check the property, separately
Knowing someone is real does not show they own the flat or have the right to let it. Ask to see it in person, ask for proof of ownership or an agency agreement, and check the address exists as described.
Do not pay to view
A deposit or holding fee before you have seen the property and a written agreement is the point at which most people lose money. A genuine landlord can wait for a viewing.
Share your own details carefully
You may be asked for identity documents too. You can prove you are a real person without sending copies of your ID to someone you have not met.