Surah Al-Baqarah 1-10 on loop (15 minutes) for memorization
To be able to focus in Salah it is better to change the ayah we are reciting from time to time. Memorizing Surah Al-baqarah even just the first 10 verses will benefit you immensely. I found it useful for concentration. Also memorizing is healthy for the brain and calming for the soul.
