The verb tenses within a sentence should be compatible. (See Parallelism.)
Margaret wants to go to a movie today, but I wanted to do something outdoors.
The students were whispering to each other when the professor spoke.
As well, you shouldn’t unnecessarily switch verb tenses within the text.
Once upon a time there was a little dog. The dog was black and brown, with some white stripes. The dog likes to walk in the park where he can chase squirrels.