Hello.I am a Jew and I have a girlfriend from Azerbaijan who goes through bad times.I would like to ask what prayer can I say every knight that will help her.Thanks for your attention.

A good prayer for anyone who needs salvation is Psalm 121,(as well as any of the Psalms). However it is better to say it during the day because there are different G-dly energies at different times of the 24 hour cycle. The energy in the evening is the attribute of  Din, Justice or severity, while in the daytime it is loving-kindness, Chessed in Hebrew.

You do not say where you live, but there is likely to be a Chabad House somewhere in your area, and that is a good place to ask for more information.