Here’s some video links to help with your foot issue and also other exercises for post stroke recovery. In most exercise I do these days, I tend to go until the muscles tires/burns rather than to a count of 10 or 20. But a good rule of thumb is 3 sets of 5-10 to begin with, depending on your level of ability. And a 1 minute rest between each set. Gradually you increase the number of repetitions in each set over time as they get easier for you to do.
Another good one I used to do to correct my foot was this one below. It’s called the “plantar fascia wall stretch”. That’s a very good one I used to do throughout the day. I was always finding places to tilt the front of my foot on and move into this stance, it became a bit of habit. And I still tend to do it when I’m waiting on things 
The gate belt this guy uses and refers to is a very good tool to have, a trousers belt would be a useful alternative, or a long scarf or towel.
If you scroll down the page in this link 
you’ll find lower and upper body workouts for after strokes which includes things like foot drop.
https://www.youtube.com/@PostStrokeOrg
These are the Stroke Association workouts set in 3 levels of ability Red, Amber, Green. Certainly within the Red programme you should find some suitable exercises for your foot.
Red group - Exercises for stroke survivors | Stroke Association
Exercises for stroke survivors | Stroke Association
Lorraine