Overgrown Garden, PLEASE HELP!!

Hi,

I am a very inexperienced gardener who is about to take on a huge job in attempting to return
the jungle behind my Mums house back into a garden.

About the job
-The garden is hugely overgrown with weeds (mainly nettles) etc...
-It is a very large garden (200 sq M approx)

I would like to complete clear the garden of weeds etc.. and start again; eventually laying turf, plants etc...

I have been told one way to do this would be to cut down the weeds and nettles, use a rotavator/dig up any roots, use a flame gun to kill them off and finish the job with some chemical weed killer.

Questions
Please can anyone advise if this is the best way to tackle this job?
If I use chemical weed killer when would I be able to lay turf? (I understand t may be a while)
What would be the best weedkiller to use?
Should I use a rotavator or will this just help spread the weeds?
Is there a better way to do this?

Basically any help/ opinions will be much appreciated!!!

Thanks