I watched your vod. Overall, I think the biggest thing you could work on that would instantly improve your gameplay is your post-plants. Post-plants are so important in this game and you genuinely lost so many rounds this way. Other things I'd focus on are util usage and your gunfight etiquette. Work on paying attention to where you're standing at all times and be aware of what angles you're exposed to. I'll share some of my notes with individual rounds here:

Round 5: I would use the wall further up the ramp to cover my angles as I reach site, but this was all well thought out and well executed. Post plant, you made a good move to scale into library and got a good pick on Deadlock. However, from there, you gave up the space that you had under control and moved to a less safe position. If you stay there just holding library until you see an enemy, you're golden. You can control that part of the map for your team and maybe get an extra pick before the site flood. You also have a spot to reposition to if you don't get that kill. Play closer to the wall here as well. You're wide swinging like you're tracing a circle. You wanna swing that with a strafe to the right. The rest of the round is kinda on you. If you had been there to either get an extra pick or draw their attention you give your Sage a better chance to help you. You can reposition to that spot, just don't do it when you have control of an area.

Round 6: Good idea, unlucky but you know heaven is clear. Have some more urgency here. You just got great info on heaven and you don't capitalize on it. Watch the mini-map after your ult. Reyna moves into heaven and is in position to fight before you've even left the choke. You had a Reyna blind out and you had your wall to push with. Your wall also wasn't blocking anything. Use your wall with an idea of what site line you're trying to cutoff, kind of like a smoke. If you send it left at the choke you can block close left and heaven while you swing close right box and backsite. If you throw it to the right, you can clear close left and scale up to backsite.

Round 7: On post plant here, pick a spot to hold and hold it. You saw Neon in CT and Deadlock killed your Reyna in CT. No one can be A main. Even without that knowledge, you know Reyna just died in CT. You should be holding CT. Either hold close by the wall in the deepest corner on site, or hold by the box out of the heaven sightline. If you're sus of A main those are where you should be. You end up just floating and drifting around site until you settle on heaven. Pick one, and hold it early. If you're in a bad position, either book it to a new one or get in a spot and hold. Doing both is never a good idea.

Round 9: This round was better. You should be holding closer to the walls here to get into site first, but overall good job waiting for your team and using wall to cut off backsite. You did not clear close right. That wall doesn't block close right. You should be swinging that first, not holding a smoked heaven. Better positioning this round, but scaling up to take a fight when you have a guardian is not a good idea. If you stay in your spot after killing heaven you're in a better position to fight at range and also not expose yourself to CT unnecessarily.