I could get your query to produce any results - here is my starting point:
index=* OR index=_* sourcetype=Terminal.debug OR sourcetype="PaymentGateway*"
| eval Action =case(match(Info, "^ApplyPayment\(\) - ManagerId.+PaymentId"),"StartTran" ,
match(Info, "^Done with Merchant lines"),"EndTran", match(Info, "^Exiting"), "Exiting",
match(Info, ""), "Info", 1=1, Action)
| eval EventTime=strfTime(if(in(Action, "StartTran", "EndTran"), _time,""),"%Y-%m-%d %H:%M:%S.%3N")
| reverse
| search Action= "StartTran" OR Action= "EndTran"
## this is wrong I need to see what is between these to times....
| sort 0 _time
| stats ????
| table _time Action Info
... View more