Here is the original item:
Jaime grabbed the leash with both hands and threw his weight backward. To
keep Roxie, his German shepherd, from attacking Mr. Velasquez, who was walking
down the sidewalk.
You chose to connect the infinitive phrase to the main clause in front, like this:
Jaime grabbed the leash with both hands and threw his weight
backward;
to keep Roxie, his German shepherd, from attacking Mr. Velasquez,
who was walking down the sidewalk.
Unfortunately, you cannot connect these two parts with a semicolon. Review the rules.