Extensor Tendonitis (?)

hi!! I have diagnosed myself with extensor tendonitis for the 3rd time since december 2024 /: it flares up pretty quickly where one run will take me out for a month, with at least the first week of that month it hurts pretty badly to walk. it’s always my left foot and I’ll get sharp pain on the top of my foot (dulls down as the month goes by) along with some swelling. I never had this issue before december 2024, as I’ve had shin splints in the past but nothing in my foot. this most recent time I stopped my run before it got too bad so it’s not a sharp pain when I walk, but it’ll hurt usually going down stairs and sometimes if I stand on it and then shift weight off of the foot. I’m supposed to be running the BSR in 2 weeks and I’ve gone 2 weeks without running. any tips for improving recovery or exercises I can do to strengthen whatever is causing this?