it is good to relax by using the internet or watching game s

it is good to relax by using the internet or watching game shows为什么会有by,后面的动词为什么加ing?
exercise such as playing sports is 可不可以把is提前到exercise的后面?
还有还有and you can spend time with your friends and family as you play together是什么意思?那个as又是什么呢?请赶快,-）