Despite the heavy rain / we decided to go for a walk /

Solution

In this sentence, the issue is with the parallel structure of the verb forms. The first part of the sentence is "we decided to go for a walk," where "decided" is followed by the infinitive verb "to go." To maintain consistency in structure, the following action should also use an infinitive verb form rather than a present participle. The correct sentence will be- Despite the heavy rain we decided to go for a walk and to enjoy the fresh air after being cooped up inside.