Do I have to report pension income in German on my tax US return?

Yes, if you are a US resident then you will have to report your worldwide income.

Pensions from the German government are treated just like US social security payments reported on an SSA-1099 (Publication 915 2022). Enter the amount received as an SSA-1099 by following the steps below:

1. Open your return
2. Click "Federal Taxes" from the top of your screen
3. Click "Wages & Income"
4. Click "I'll choose what to work on"
5. Scroll down to “Retirement Plans and Social Security” and click "Start" next to "Social Security (SSA-1099, RRB-1099)" 
6. Answer “Yes” to “Did you receive any Social Security benefits?”
7. Select “Social Security benefits (Form SSA-1099)” and enter the amount in box 5

Please see Is my Social Security income taxable? for additional information.