Arround TXL is a lot of construction at this time. Expect traffic delays. IMHO No chance to get your flight.

However, if you're lucky and have checked in online and are travelling only with hand luggage, 10 - 15 mins are fine. KL has a gate position at TXL and there is no airport in this world with shorter distances to the plane.

As to my experience even if you miss your flight, KL is quite generous to skip the rules and put you on the next flight, if space is available. Never heard of anybody having to pay a new ticket because of a missed flight. Even with the cheapest V-tickets they rebooked me if needed free of charge. Since AF has the handling of KL this got even much better. BUT. Thats for me, and I am Platinum.