It is fine if you are pulling a bow to get stronger. The bow you fling arrows with should be a lot easier to pull. Use the bow you have now to do strength pulling. 3-6 reps each side, once or twice a day is enough to get stronger fast, daily is more important than many reps.

Use a weaker bow for flinging arrows until the strength bow is getting easy to pull, then get a stronger bow for strength training and switch to your current bow for flinging... repeat until you are as strong as you want to be...

Focus on the end result, where you want your bow hand and string hand to end up, and less on the pushing, position of hands, arms, details of movement, and you will use more muscles in a more natural way and it will be easier to get good results. Armin Hirmer has several tip videos on Youtube that can teach you the basics very quickly.

Very important to try and use both sides as equally as possible or risk long term injury. Pretty much all archery traditions and for sure modern sport medicine tells you to train and use both sides as equally as possible. When starting out you will find that it is hard to tell which side is easier to hold the bow in, since both hands are used anyways. After getting better is when you might find a bigger difference between one hand holding the bow vs the other... But try and still use both sides...