I improved a great deal from finding partners who pushed me. I had one RP that started off Free, morphed in Casual and in the end, became a full blown Advanced thing. The plot and partner really made me invest more detail and develop into the big picture. It was a lot of fun. As others have rightly suggested, you just need to practice. And also read and write on your own. Even if it's just a flash fiction or short story, sometimes people improve on their own while others need outside people pushing and cheering them on. If you want a buddy to 1x1 with, I have a lot of free space on my RP Plate, so to speak. It's great you wanna improve, don't give up. :)