Hello @SAYED_ALI,
It will depend. Did you follow the Bitnami Doc to create the renew script and crontab entry?
@rg305, thanks for pointing to the official doc 
As I can see, that doc says that you must stop the bitnami services, renew the cert and start it again, I mean, it doesn't check whether the certificate will expire in x days and in case the certificate should be renewed then it stop bitnami services, renew and start, no, it always stop bitnami services, renew the cert (because of the --days 90 option) and start the services and does it the first day of month at 00:00.
0 0 1 * * /opt/bitnami/letsencrypt/scripts/renew-certificate.sh 2> /dev/null
So, it is not the best way to renew the cert because it always renew the cert every 1st day of month and it must stop the services (so there is downtime) but if that is the official doc to issue and use a cert in your bitnami services then go ahead and use the parameter --days 90 and the crontab entry shown in the documentation.
Cheers,
sahsanu