Ive just bought an a3 sline 2007 with 190k miles I bought it from my hart not my head what can I do to the engine to have peace of mind it will run for another 70k please need some advice thank you 

Well, I'd advise speaking to Audi to see what service history they have on it. That'll give you some service history at least. 

But with no history, you'll need to do a full service including Cambelt and water pump change. You may as well change the thermostat whilst you're at that. Then do a gearbox oil change too. 

Hello Jason, 

Many thanks for joining and posting your question.

Although that’s a high mileage for any car, it’s not to say the engine won’t continue to give good service - but for another 70k -? 
You don’t give us much to go on Jason, to be able to advise - petrol or diesel, your anticipated annual mileage, typical journey length, whether you do your own servicing and repairs etc. etc.etc? So answering your question is a bit like like waving a magic wand. 
Apologies if it goes without saying, but although an engine is a major component, every other moving component on the car will wear/ be worn, so you will need to assess the serviceability of everything else. 
My suggestion is to have the car ‘health’ checked, or if you are able - fully assess it yourself. Following that, I too would do as Steve suggests. 
Perhaps you could let us us have the answers to the questions Jason. 
Kind regards,

Gareth.