Yes, it is ok. Here is another way you could say it: "I noticed a little girl crying beside the road. Seeing no parent nearby, I decided to take her to the police station." Since you are telling the story from your point of view, it works best to start with "I noticed" rather than "there was". "There was" sounds like the beginning of an impersonal narrative. Also, without "noticed" the sentence contains no verb other than "was". The verb is usually the most important word. Verbs describe the principal action. "Crying" is an adjective describing the girl, not a verb. The narrative of your story is carried by the verbs: "I noticed"...."I decided". Your second sentence is fine, but it is really a compound sentence. In other words, it is two sentences. Saying "I" twice in one sentence feels a bit repetitious. A good strategy to use in situations like this is to pick out the most important part of the sentence ("I decided...") and make it the dominant clause. The "dominant clause" is the part of the sentence that contains the subject and the verb. Then, you transform the rest of the sentence into a clause (or clauses) that modify parts of the dominant clause.

It's perfect. It sounds very natural. I like the way you wrote it better than either of the other suggestions you've been offered.

Yes. It works well. You might use a modal verb ‘couldn’t see ’. Instead of ‘didn’t see’ to highlight lack of ability rather than plain fact. Otherwise it’s good.