Roof on home in OK leaks in 5 places aftr storm. Options?

this 2 story beauty home (1993) has 4-5 leaks!
Leaks thru aftr storms.

…the pitch of the roof, they recommend 5 nails for shingle.
They think that the builder-roofing company probably only used 4 nails per shingle and that is why the shingles are sliding down the pitch of the roof and causing leaks in those areas.

What is a durable, good looking, options that is reasonable
**Is a Metal "shingle roof"put on top of orig roof a good idea?
Any suggestions, what costs could be?

How many nails will not make a leak, where they are put will tho. Send us some pitcures so we can have a guess at whats wrong. It could be a million different reasons.

If the nails are high then that could cause the shingles from sliding down but some pictures would help alit. I am just specualting.