Hello and welcome to the forum
Where are you located? Someone local to you may be able to give first hand help. It is a little difficult to diagnose issues in text but we will try.
There could be a number of issues, carb settings way off, glow plug dead, glowstart battery flat, engine flooded, no fuel, air leak..... list goes on.
As suggested it does help to pre warm a new engine if the pinch is very tight but starting can be done without. I wouldn't leave the glowstart on for an extended period of time, it's a sure way to kill a plug and only shows the engine is way to rich. Even for breaking in.
I find pullstart better as you are able to tell(through experience)what the condition of the engine is.
When you say the engine is cutting out after 5seconds are you just letting it sit at idle or giving it a little blip of throttle?
My guess is the carb settings are overly rich and the engine if flooding, then you try to restart without ridding the engine of the excess fuel. This will give no chance of starting it.
Does the pullstart get harder to pull once it cut out and you try to start again? Is there unburnt fuel exiting the exhaust?
Persevere, we where all here at one point. It's worth it in the end!