Can I make dua for a friend who was still unsure about Islam?

Assalamu alaikum. I don't usually post online, so sorry if this seems messy. My close friend, who was 17, recently took his own life. He had been learning about Islam for a year and sometimes called himself Muslim. He even went to Jummah prayer at the masjid a few times. He was raised Christian, but he felt more drawn to Islam. As his mental health got worse, he stopped calling himself religious, but he still respected Islam. After he passed, his family put a Quran and a Bible on his bed because his father raised him Christian, but my friend owned the Quran. He wasn't a full disbeliever, but he wasn't fully Muslim either. I'm grieving a lot and just want the best for him. Can I pray for him? If not, is there anything else I can do?