Hi Dango,
Ok, so there are a couple of things that can really help you in this situation. Firstly you need to think about the depth of your first loop on the table, if your forehand loop is landing short on the table it will be easier for your opponent to punch the ball back strong. So have a look where your loop is landing or video record yourself playing so you can see, if you can get the ball deeper on the table with spin it will be much harder for him to play strong. In addition make sure you aren’t lifting too much up the back of the ball when playing the first shot, ensure your bat is still brushing forward to keep the ball low and hard to counter attack.
The second is the variation of spin and speed on your first loop, quite often with players who punch/slap like you mentioned its variation they struggle with, so mix up the speed and spin on your first loop as well as direction. This forces your opponent to adjust a lot more for each shot and deal with the different pace/spin coming at him.
Give that a go and see if you have more success! Tom