My father is not regularly performing the five obligatory prayers but he helps the poor and is very kind.
Will he go to hell or paradise according to the sharee’ah?

All perfect praise be to Allah, The Lord of the Worlds. I testify that there is none worthy of worship except Allah, and that Muhammad is His slave and Messenger.

Allah is The Only One who knows the destiny of His slaves. It is Him who knows who will go to Paradise and who will be sent to Hell.

As for the Fatwa on those who neglect the prayer, we refer you to Fatwa 85264.

We remind you that nothing brings the person closer to Allah more than what Allah has prescribed on that person.

Abu Hurayrah narrated that the Prophet said: “Allah said, 'I will declare war against him who shows hostility to a pious worshipper of Mine. My Slave does not get closer to Me with anything more beloved to Me than something that I have enjoined upon him, and My Slave keeps getting closer to Me by performing Nawaafil (supererogatory acts of worship) till I love him, and if I love him, I become his hearing with which he hears, and his seeing with which he sees, and his hand with which he strikes, and his leg with which he walks; and if he asks something of Me, I would surely give it to him, and if he seeks My Refuge (protection), I would surely protect him (i.e. give him My Refuge), and I do not hesitate to do anything as I hesitate to take the soul of the believer, for he hates death, and I hate to disappoint him).” [Al-Bukhaari]

So, the rank of Nawaafil is lesser than that of the obligatory acts.

So, you should advise your father and remind him of The Last Day and clarify to him the great position of the prayer in Islam.

Try to profit from his good deeds and build on them.

Allah knows best.