I want email will be sent only one time when payment will be successful, don't want to stop the sending process of order confirmation email
You can do it easily with
disable the order confirmation email from admin and
enable invoice email from admin.
So it will send email at the time on invoice (payment received) only and not sent the order confirmation email.
Order email setting, Set it to No :
Admin -> Stores -> Configuration -> Sales -> Sales Email -> Order -> Enabled
Invoice Email setting, Set it to Yes ::
Admin -> Stores -> Configuration -> Sales -> Sales Email -> Invoice -> Enabled
You can change the invoice email content as per your need.