Bad news:
We changed the delta process to "AIED":
We re-installed and activate "3FI_GL_0L_TT". Data source can be selected within Theobald XtractIS (Xtract IS - Theobald Software GmbH). Init delivers the correct amount of items and sums fit to different existing SAP customer reports. Furtermore data source is visible with status green within RSA7.
Safety interval is the defaul value (No specififc settings for "3FI_GL_0L_TT"):
Within IMG (SPRO) evething seems to set-up correctly but maybe a wrong settings within IMG is the problem?!:
Table "FAGLFLEXT" is filled (also column "TIME STAMP"):
Extract stucture and extractor is avtivated (TCODE "RSA2"):
Created two document postings with TCODE "FB03". Posted values are effected directly within SAP when calling different SAP reports. Waiting 1 1/2 hours and start delta extraction but no records were extracted 
I am despair ..
Are there any dependencies to the Line Items DataSource "3FI_GL_0L_SI" (Sequenceofextraction e.g.)? How can I check that the new created documents are contained within table "FAGLFLEXT"? How can I check if the delta pointer is TIMESTMP?
I hope someone can help us to find the source of the problem.
BR
Florian