Please correct these sentences:

1. We played paintball. I decided to give up, feeling a strong pains in all parts of my body.  "surrender" would be appropriate in a military context.  "surrender" could be used in other context too, but in the context of a game, "give up" is commonly used.
2. I eat oatmeal every morning, and I slowly accustom the baby to eat a porridge.
3. Parents often give in to their kid's whims, and give them permission to do what they want. 
4. A/The robber had grabbed an ancient coin and disappeared.  By using the past perfect tense, it means that something else happened after that.  Example:  [Ten minutes before the police arrived, the robber had grabbed an ancient coin and disappeared.]
5. She said that he [she???] is very vulnerable and hasn't any courage, so it was a challenge to revenge her.  ... so it was a challenge for her to take revenge.  ???  Sorry, I don't really know what you want to say.  If you paraphase in English, or write the sentence in Russian, I'll try again to help.
6. He had stumbled and tumbled on the ground.  
7. A consumer is always right.  We usually say it like this:  "The customer is always right."
8. Don't abuse/mistreat poor animals. They are innocent, and live in their own habitat. It is you who came to their home.    "offend" applies to feelings and emotions.
9. A vampire died, but afterwards he was resurrected, and he will drink another blood again tomorrow night.