should i do box squats and how often???my form is decent i think..will it help me?
In your particular situation, which you so precisely described, Id say yes, absolutely. I also deduce from your post that you need to do two more sets of triceps extensions on fridays.
There are a lot of different factors to be considered here. What does your program look like right now? What are your goals? Do you want to compete in powerlifting? If so, raw or geared? If you answer these things people can give some feedback.