Is it possible to get pneumonia more than once? If so, is it worse the second time (i have lung scars) or better (immune system memory)?

Pneumonia. Yes, you can get pneumonia more than once as pneumonia can be caused by many different viruses, bacteria, fungi, parasites, chemicals, aspiration of stomach contents, etc. Every time you get it, it can be just as bad. If you have problems with your immune system, you might be particularly at risk of getting pneumonia more than once and also pneumonia due to opportunistic infections like pcp.
Yes, it is. Pneumonia isn't a specific disease so much as fluid collecting in the air spaces of the lungs. This can be caused by a wide variety of pathogens, some of which we become immune to (some viruses) but many of which we do not (bacteria, mycoplasma, etc). So you can have pneumonia multiple times. This doesn't mean that future cases will be better or worse, although bad cases can damage the lungs.