as salam alaikum
a way to strengthen our own faith is constant prayer and recourse to Allah in our heart by speaking to Him and sharing with Him our fear, pain, joy, hope, etc. and continuously asking for His guidance.
Continuous repentance is also very effective in this regard.
Furthermore it is good to help other with a pure heart by giving charity keeping in mind that charity is not just giving money but also your love and assistance to others for Allah's sake.
In this way, Allah may increase the faith of His servant and make him more aware of His overwhelming grace.
With prayers for your success.