Berlin airport ist far away. With a regular taxi you pay above 60 €. The highway is often congested.
If you don’t have a lot of luggage, small children etc, the best is to take public transport with S-Bahn or RegionalExpress or FEX (Flughafen Express). Google Maps can show you the best ways. Enter in the details at what time you want to arrive. We recommend 2,5 hrs before the departure. The price is 3,80 € p.P. one way (12/2022). It is by far the cheapest possibility.
Book a “runway” Security slot at the Berlin airport before you go to the airport: https://ber.berlin-airport.de/en/flying/controls/security-control.html#runway
This is like fast lane. It reserves you for free the security control.
The City Railways are the most reliable as they have their own tracks, BUT also here you can have bad surprises. Everything is possible! It’s Berlin!
If you have sufficient money, children or lots of luggage or what ever, I recommend you to book a Van. We always book the Taxi Van of Mr. Akca. He charges 60 € flat, which is the similar to the average price for a taxi., but without the risks of being stuck in a traffic jam and paying high fees. So he monitors by himself the traffic and tries to find best ways. It happens that he called us and asked, if we can be ready earlier as there are bad jams. He takes you to and from the airport. He has a clean Mercedes Vitobus, for 7 passengers + luggage. He does have child seats.
You book him comfortable via WhatsApp: +49 176 68183029
With regular Berlin taxis I made bad experiences, as they did not take the shortest way, charge extra for suitcases, have dirty smelly cars, are unfriendly etc.
You also can use car share cars as Miles or ShareNow, who have their own parking facilities near the airport. I find it a bit uncomfortable
Of course, you can check Uber, Freenow and Bolt. But even with their promotions they are hardly below 45 € but often over 60 €. So I just book Mr. Akca for peace of mind or, if I am alone without kids, I take the S-Bahn.