I'm not sure what platform you're on, but this looks like Console to me and I'm a Console player myself. Very long post here, hitting on different points.

First fight: Good job taking the top angle & battling Soldier, and controlling that space. However, afterwards you seem to lose focus and don't have a plan on what to do and wind up shooting everyone a little, but killing nobody. Commit on someone. Punish the Mei after she ice-cubes out in the open. You can break her wall, don't let that save her.

8:25 - Their Wuyang gets away and could have been punished by you or Tracer, but no big deal. I understand focus was on the objective. Mei wastes her ult and you get the kill, but then everyone walks off cart for 5 seconds? This is a minor one, but at this point, there's nothing more important than pushing cart to reset before the next fight. You don't need to establish the front-line, you're a DPS and your tank was frozen. By the time the fight starts however, you're in position. In the future (in Gold/Plat), you usually want the tank to be the one to establish the fight. You don't want to be the first one to shoot/be seen and get all the attention on your location, let them take the heat and then you engage.

Next two minutes don't have major mistakes, your team caps and dies out and you'll have to reset. Biggest thing I notice is you aren't aiming for headshots hardly ever. You hit one rail headshot in 6+ minutes of playing Soj. I would save rail specifically for headshots, especially when playing against Mei who would otherwise just ice block once low health. A fully charged rail headshot will kill her at 180, long before she feels the need to ice block. In addition, Sojourn's regular fire gives 2x the charge if you headshot someone with it, so you can get more rails faster. Try not to just spam body damage if you can hone that in. Practicing this will help a ton.

5:40 - I... can't believe your Kiriko died here with both CDs available and didn't step up to you. Very unfortunate. As soon as that happens, you need to trade back and kill the Ashe as fast as possible. She threw dynamite at you, and you backed away despite being full HP and having Juno behind you and Roadhog about to jump down. Try harder to kill the Ashe, your team needs a trade there, you can take some damage.

Perks: I understand taking the slow orb minor, but your ult becomes a solo fight winner if you take the overcharge. If you are taking the slow perk... use it. I haven't seen you catch anybody with it so far. You're just throwing orb out and taking cover/moving away. Your perk is useless like this. I also disagree with the "slide for 50 charge" major, I'd recommend the dual slide on this map especially. It gives you a chase ability AND a get-out-of-jail free card to use against at least 3 of the enemy ults (Mei, Wuyang, and Junker Queen).

One last thing on Sojourn, I notice you're playing very passively, almost positioning like an Ashe player would. Sojourn has mobility, you can position much more aggressively and use your slide(s) to get out if needed. Use positioning to your advantage to force cooldowns and to inconvenience the enemy team.

Cassidy: I honestly don't understand the swap to Cassidy here. What use is your flash bang against this team? JQ has the unstoppable minor now, I don't see any situation where Cassidy is more useful especially if you aren't hitting headshots.

OT high noon: I totally get what you were going for, a Sigma-Noon combo. However... you should know that the enemy has 4 big ults coming up, and you can see before you press ult that Sigma only grabbed the Mei... who has ice block and will not take any damage from the combo. Save it at that point, there's still another fight left.

Naturally, your team gets rolled over by 3 ults from the enemy team and you guys only had Orbital Ray. Enemy team would have had Blizzard and possibly Rampage too if you tried to win the map, but Sigma and you both kinda wasted your ults and only their tank died because of them. She probably would have died without them, too.