as a beginner, how can i improve??

i have around 140 hours in the game and im 5K premier rating. i usually the worst or second worse in the server, and when im not, its because of a lucky 3k or so. this is my last premier game as an example steam://rungame/730/76561202255233023/+csgo_download_match%20CSGO-rEzj5-FGThG-UcdvE-Kb68k-uXNtQ .thanks!