Writing in chronological order using past participle and simple past

Hello,

Please, I need to prepare a story about buying a dog. The excerpts in this story turned out differently than i expected using events in chronological order like first of all, next, then, later, and finally.

I was working on something,but on unpleasant situations...Please I need an extra help for finish my story. And finally, i´ll need a moral for my story..thanks

"One of the biggest mistakes I´ve ever made was buying a dog. I always wanted a small one like a pocketpet I´ve seen long time ago. I still remember the day I bought my dog. It was the happiest day on my life..and everything turned out differently than I expected.

First of all, the dog dirtied my room. As I didn´t take him out for his pee, he peed under my bed and near the door.

Later, when I was trying to walk my pet around the neighbourhood two big dogs chased him to bite....(i stuck here...help me pls)