I'll say first that for the sake of improving, it's usually better if you show a game you'd consider your performance more average. If I'm watching a replay where you get curb stomped repeatedly or where you don't get contested much, chances are it'll feel like there are fewer unique situations for me to talk about. Ideally it's a very back-and-forth game. There still are things to talk about here regardless.
The first point in the game I want to bring up is around 30 seconds in, I would be a bit more mindful of that Trizooka if I were you. Once that first shot fired, the moment you could have reacted, I probably would have gone into swim form and dove behind the wall to your right that you do eventually walk behind. Maybe the ledge behind you instead if you still wanted to shoot at people but that is a little bit riskier in this case. If you're playing a longer-ranged weapon, you're going to be a Trizooka's primary target, as you're the most difficult weapon to approach and are often standing in wide open spaces that are easier for a Trizooka to hit.
From what I gather here, the first point you die is from you losing your footing and falling off of a platform, then panicking when an Inkbrush ambushes you from above. Mistakes happen, but you still did have a bit of time to act before they killed you. How quickly and what you do in situations like this will come with time, but there is a nice trick that can help in a lot of them. Try thinking of a direction you want to move in, then holding the control stick in the opposite direction while shooting your feet, going into squid form, and finally flicking your control stick and squid rolling in the direction you want to go in. It's much harder for your opponents to paint your feet when you do this because most of your time here is in the air during the squid roll and you get a bit of extra HP there too. In this case I would've considered squid rolling under that glass tent or just headed back where you started.
Also, don't forget to use full-charged shots! There were a few points I saw you firing your weapon at a range that was just out of reach of the enemies. Creating a wall of explosives that they would need to take big damage to go through can be very nice sometimes, especially if your shots wouldn't be able to reach them otherwise.
Second time you died was just a matter of not keeping your teammates between you and your opponents. You mostly did a very good job of this during this replay, but here you tried getting on the Tower even though you could see an enemy standing on it. The Wellstring doesn't really like playing as close to people as you would've needed to in order to win that 1v1 with that Splattershot player. The situation wasn't super urgent since you weren't at risk of them taking the lead had you lost that fight. I would've just backed up a bit and tried shooting them from a distance while waiting for my teammates to get back.
A small tip with Ultra Stamp. If you jump and then hold down the button to start swinging, you'll start attacking a good bit faster than if you just hold the button down while you're on the ground. You're a bit vulnerable otherwise so it's worth a mention.
Otherwise, like I said before, you mostly chose good spots to stand in and you also got some nice kills here. Good job this game. I think just a bit more play time could help you a lot here just to get a feel for some of the situations you found yourself in here. If anything doesn't make sense here or needs further explaining, feel free to just ask! To both you and anyone else reading this - don't hesitate to reach out to me with another replay if you want that reviewed. I've done this twice in the past two days funny enough and have enjoyed doing so both times!