Replication oplog window has gone below

Hi Team,

Replication oplog window has gone below 72 hours frequently received alert , we did check in logs and oplog collections insert and update and recently changes not much affect very less changes but considered getmore and query going between 120 140 and more per second these commands appear Opcounters metric when we received the alert

so what is factor any additional we need to check replication oplog window has gone below ?
oplog size : 38000MB oploggb/H: 700

In oplog collection filter condition query taking long time how do we retrieve data from oplog collection with short time