For Du’as, I recommend you recite one of the 15 Munajat of Imam Zainul Abidin (a) every night. Read them carefully to see what they mean, then read the Arabic. It will transform your life.
As for the app, as long as you don’t believe it actually uncovers your personality traits in the form of unseen factors, it’s ok to use it. You can read the birth charts for fun, but don’t believe that it is accurate and true.