This is the 7822nd most frequent Spanish word.
mantenga
"Maintain" or "keep" (third-person singular or formal command form of "mantener").
Here, 'mantenga' is used as a formal command to mean 'keep' or 'maintain' something in a certain state.
Por favor, mantenga la puerta cerrada.
Please keep the door closed.
In this case, 'mantenga' is used in the subjunctive mood to express an action that is important to happen.
Es importante que mantenga su palabra en los compromisos.
It is important that you keep your word in commitments.
Here, 'mantenga' is giving an instruction in a formal manner to perform a specific action.