That's where I was talking about the throttle roll off. You have to allow the engine to settle after you build up the speed near the top of the RPM you targeted to shift at. The more throttle angle you apply, the more roll off you need to allow to level off the fuel to minimize rev hang.
One thing you can do is after you engage 1st gear, give it more gas as you normally would to accelerate and just hold the pedal steady until the engine reaches the max RPM for that throttle input, and hold an extra second. The engine by then has settled to the max RPM you targeted for that throttle angle so you won't have to roll off the throttle and just continue onto shifting into 2nd gear. Once you get the hang of that, reduce the extra duration you are holding the RPM in 1st. Once you get use to that, then you can drive more dynamically by modulating more throttle as needed and roll off without thinking about it.
I think you are modulating the throttle too much and possibly feathering the clutch which is both unnecessary for a beginner.