to have uncertainty regarding something
Zweifel an etwas haben (Zweifel an etwas haben)
"I have serious doubts about his honesty."
"Ich habe ernsthafte Zweifel an seiner Ehrlichkeit." (Ich habe ernsthafte Zweifel an seiner Ehrlichkeit)
to withdraw investments or operations from a market
to use your past achievements as a base for further progress
to acknowledge achievements in front of others
to change behavior or methods based on what one has learned
to maintain economic progress over time
to go beyond limits or expectations