Car will not start after driving few miles.

Hi, many thanks for reply. I have a little update to the story.
It did not help.
I think my describtion of the problem was slightly wrong in the first place.
When it is cold engine it is turning over and starts usually after two to three seconds after turning over repeatedly. When engine is warmed up and I switch off the car and try to start it again soon it is turning over but there were four occasions recently when it was just turning over constantly and did not start.
Second mechanic cleaned all the sensors - crankshaft etc. And it did not seem to change anything. Before leaving him I just remembered very vital piece of information. When I changed fuel filter two months ago (after not changing it for at least six years!) It was okay and car started instantly but it only lasted few days. Then problem reappeared. I mention this to mechanic and he took it all out checked inside, everything seemed to be fine. He did put it back as it was and car started without any problems again, but again for couple of days only.
So the problem seems to be around fuel filter and fuel pipes I believe. I bought today new fuel filter to replace it again and also STD diesel fuel injector cleaner. Not sure if that has anything to do with it but I thought for  5 it is worth to give it a shot. In few days when I go down with fuel in the tank to minimum. I will fill up with the best diesel out there like shell vpower or something like that and will add this cleaning liquid. I hope that will help but in the meantime do you have any other suggestions after I described the problem in more detail?
Also, is it better to put cleaning solution first and then change fuel filter after few days or change filter and then put cleaning solution? Thanks

I do not think they did. I put the cleaner we will see after tankful.

In my model of Astra I do not have a pump apparently. That is what one guy said who came to check for pump issue.