Dear day doctor I want to know how I can ...

What is the normal penis size in relax and erection time :
1. erection : 8-18 cm
2. relaxtion : at least 6 cm
Does penis size matter ?                       
penis size matter if your current size isnt within normal range , but if its within normal as majority have, size doesnt matter and there are other factors that are more important such as :
1. sexual intercourse techniques 
2. ability to satisfy your partner 
3. relationship with partner ( no tension , good relationship ) 
4. creativity about your sexual life , such as trying to renew it and using different methods and themes or ideas for sexual satisfaction 
regarding increasing your penis size without side effects :
there is no recommanded products or methods as its all totally unreal claims , there is no cream or machine have the ability to increase penis size , and its all false claims 
- some product may help with sexual energy , but cant increase penis size 
- the only proved way to increase penis size method is by surgery and it have side effects and complications are all surgries do