Need help with a few features on website

Hey I’ve been trying for hours just to add a few finishing touches for my website I am working on. I can’t figure out how to get this certain design working.

Here is an example of what I am looking to do

1 - I am trying to get the navbar to be clear and when I scroll down, it blurs out what it goes over

2 - In the testimonial section: How to add that blurred effect on the “next” and “before” testimonials.

3 - In the smooth hiring section: How to make it so when you scroll down, only one block is shown at full opacity, while the others are a little faded out

4 - In the smooth hiring section: How to add that numbers effect as you scroll down the page
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If anyone could help me with this that would be amazing! I hope I explained what I am looking for well. If there is anything else I need to re-explain, please let me know. Thank you so much!