Enroll via the link above (Use Chrome Translate) and you’ll get 4 months of free Air Berlin Silver/OneWorld Ruby Status.
Allow a few days for your status to be upgraded.
American gives a free checked bag and priority checkin and standby for OneWorld Ruby elites. Just enter your Air Berlin mileage number when flying American for those benefits (and change your number to American at the gate to accumulate AAdvantage miles if you’re on a paid ticket).
You should also be able to match your Air Berlin status to 4 months of Turkish Elite/Star Alliance Silver status. If you fly on Turkish during those 4 months your status will be extended for 1-2 years. You can apply for the match by contacting them via this form and click on new feedback>Miles & Smiles>Request>Membership Processing and send proof of your elite status.
Star Alliance Silver status only gets you priority waitlisting and standby on all Star Alliance carriers, including United. That especially helps when your flight is cancelled and you’re trying to get accommodated on another flight.
Some airlines also give a free checked by to Star Alliance Silver elites. For example Air Canada gives a free checked bag though United does not.
You’ll also be able to use priority checkin, security, and boarding lines with some airlines.