Watched to your video and came to a conclusion.
Your bigest issue is enemy priotization, most kills you got were passive, meaning you didnt activly seek the kill they just walked close to you with low hp and you just gave the finishing blow who happened to be nearby.
You dont look for enemies and just push too hard hoping people will come to you, they do eventually which i would point out it was luck that you manage to kill them and survive but it wont always work (the enemy just reacted poorly)
Reaper has two playstyles either a flanker or tank busting, if your tank is unable to push you have the option to kill the supports/dps in the backline or brute force your way and kill the tank.
You get way too cocky thinking nobody will kill you, at times you just straight up die by just walking towards them, you taunted a roadhog who was at range to hook you.
Pacing is rather slow whenever there are no enemies in sight you just afk at times then ponder why the payload isnt moving then you see 3 other enemies that you left behind, if a enemy dies you instantly should look for other targets dont assume they are dead.
Positioning is important you died alot becuase you exposed youself too much you rely too much on healers to heal you that you just stand still and do nothing, if you are low seek for health packs, rarely you ever need a support to heal you because ussually you would be far away from tanks doing kills.
Okay to the mei
You priotize too much on freeze that you die, because you forgot you arent reaper anymore, she plays way different, you play her for the walls not freeze, you never used her icicle shot and just straight up walk to people and exposed youself too much.
You only need to freeze if they walk to you, not the other way around, you have to use her walls more to isolate targets. At times you just walk up to group enemies and die you should priotize more your safety and take more actions to get a better positioning.
You never used his optional ability which allows you to increase your speed gives armor and faster shoot rate.
Torb turrets works best if you are in completly opossite sides of the team, forcfully making a choice to go after your turret or your team, putting it in a hard spot where they get pincered is the best scenario for turret.
Anyway i notice you play those heroes because you are not confident in your aim.
If you are going to play heroes who dont require such high aim you should really focus on game sense, pacing and positioning, keep a goal of not dying ussually keep it below 5 deaths.
Your duo partner played really well i assumed he was silver (you already confirmed this but i already figured as much based on gameplay)
The only suggestion i make is increase his pacing speed and take more advantagueos positioning.
He needs to have more confidence in shooting the shields, at times he flat out refused to shoot it, even when ult was on, if there are no other targets, you shoot the barrier to force a retreat i think his biggest issue is that at times he will flat out ignore the tanks even when they are aggroing his tank or supports which is a no go. He could definitly reach to plat if he spend the time on gamesense, positioning and pacing, his aim discipline is really well.
The reason why you lost was becuase you didnt priotize targets, you died alot and was neglecful towards your tanks (your main tank had to fend of 3 people by himself zarya was doing all the heavy work, zen was putting discords which heavily inflated your kills (its a good thing but understand you werent the carry) and you had mercy dmg boosting whovever was the carry, rein doesnt have much support as this a damage comp all he had to do was not die and drop is his pacing lower for the low heal times he will get, rein played the minimal amount, but glad he understood what type of comp he was running, he could have played it better yes but he played the minimal amount.
You and your duo need to die less to take advantage of mercy rez you never got rezed doesn’t that seemed odd to you? you were way too deep for healers to ever heal you and didn’t utilized health packs. Think of it like this every death =6 kills you would have gotten everytime you died take away 6 kills because you lost time walking back to your team. so if you died more then 4 those 24 kills didn’t mean much.
You did not get 100 elims because its based on who has the kill lead you were behind your partner was in kill lead, you dont combine kills to get a result this overall tells the player who is the lead in kills not total elims.
Overall Die less, priotize targets and have a focus in mind that every kill you get look for somebody else don’t wait. Oh and also use health packs more and stop relying on your supports.
May i suggest hitting up on practice mode and practice tracking, strafe left and right around a targets head and try too keep the crosshair in the head its a good start to get a feel on your aim. if you keep practicing that, you will eventually get better at tracking like your duo.