Hello everyone!! I guess I’m looking for a little pep talk. I got an offer from my dream company, great position, great salary, fully happy with everything. Now I need to hand my notice in my current company. We are a relatively small team, pretty much a new department in my country, I’m the only one who kinda knows how to do my job, noone is trained to cover for me when I’m out, not by my own desire its just everyone is swamped with their own work. My boss adores me, every thing I do

If your boss is truly the amazing supporter it sounds like, he will be sorry to see you go but happy for you. Probably helpful to say a lot of what you said here- "I got a dream offer. I love working with you and would only leave for a dream opportunity. Here's my plan to ensure the smoothest possible handover...."

Don't beat yourself up. In the end, you have to do the things that will get you to the place you want to be in your career.

Sounds like you are suffering from a bit of imposter syndrome and guilt. You also sound adored at your current role so you feel bad.
Their failure to train your peers to cover for you and eventually backfill you, is not on you. You give a lot to this job and you will do so in your last 2 weeks. Use that 2 weeks to prepare the team for your departure, leave training materials for the new hire and go get your dream job girl! It may be difficult for them in the short term, but they will figure it out. People leave jobs all the time and the world goes around.

It also sounds like your current job is largely positive so they will probably be super happy for you! I know it feels daunting to give notice, but keep it short and sweet and say you’ve accepted a new role. Thank for the opportunity, express appreciation and offer to stay in touch as you don’t want to burn bridges ever. Let your manager ask any questions they have and don’t over share. I think we often assume people will be mad and take it personally, but it’s not personal - it’s business.

Congratulations on landing your team role, you deserve it!

Is a master peace and he relies heavily on me. So how do I ever tell him I’m leaving?
I feel terrible and so guilty
I literally wasn’t looking to leave unless I land a job in few of my top companies in my city, and since I managed to do that its logical for me to leave

You don’t need to feel guilty. Leaving is nothing personal. It’s just business.

You made the choice to look for, interview, and accept a new job. Tender your resignation, and create a transition plan on how you can set the team up for success until you officially leave. You are adding unnecessary layers to a simple straightforward process by focusing on these incredibly unimportant details.