I have 2007 Opel Astra 1.6 Essentia. It has a miss on low revs. I have replaced The EGR valve as well as crankshaft sensor but to no avail. do you have the answer?

Sure lots, you have misfire. when, say EXACTLY.
when does it and when does it not?
guessing is expensive?
misfires in gear or. parked in park or neutral,
or only driving?
why not do the 60,000 mile tune, why not?
spark plugs , that is top of list. not crank shaft sensors.
1: tune it up. spark parts and filters.
2: keyon, CEL glowing , check engine lamp ? good.
3: start car is it glowing now running, yes, that means SCAN it.
4: best practice would be to drive with scan tool connected OBD2.'
and watch to see if you get P030x misfire codes.
The ECU would have told you the CKP crank shaft sensor is bad or good. the ECU does that on all cars, no need to guess and go broke.
if very intermittent it shows up in OBD2 PENDINGS.
the ecu will report 1 in 10 ckp pulses, missing,(sensitive it is this monitor.

Physics.
Misfires:
1: weak compression on 1 or more cylinders.
2: bad spark, (tuneup time and scan it)
3:bad fueling, scan it. see it way off. (can be vacuum leaks)
4: coolant found in the combustion chamber, spark tips look UGLY. nasty . and repeats. with new plug. not looking is FAIL time.
5: EGR closed. at idle, so if misfire is at idle? , bam.
running the EGR is open, so its not egr, if running ,moving are you?

the above order saves time, and cash.
fuel can burn right with bad compression or spark so fueling is dead last.