Prepare to feel like an imposter for the first while. You're out of your comfort zone in stepping into this new role so you're naturally going to doubt yourself. You'll settle into it as you get used to making decisions and issuing instructions. The important thing in the short term is not to take negative thoughts at face value. Take step back and cast a dispassionate eye over what you have achieved - consider the delivery dates you've met. the positive feedback received, the challenges overcome etc.
My advice for somebody starting in a team lead role would be the following...
What's the next step? I asked myself this constantly. What's the next step needed to get this work done? Do you need to do a proof of concept? Does somebody need to research something? Do you need something from the customer? Identify what that thing is and the person responsible for it. Agree a time for delivery and touch base regularly with them to see if the time is slipping. Never assign a task to "the team" because everybody will wait for somebody else to do it - and it will never get done.
Figure out the personalities. Different people respond to different stimuli. Some will need an arm around the shoulder, some a kick in the backside. Some excel with praise and "attaboys" and others want to know they have some input into decisions etc.. Figure this out and you'll know how best to deal with individual team members. This is half of the key to the conflict resolution challenges facing you - the other being...
Be decisive. Don't appear too dithering. Your team need to have confidence in you - make decisions, make them confidently and make them reasonably quickly. That's not to say rush into it - that would be foolish. If you need to, get the right people into a room. Let them talk. Listen. Ask intelligent questions. Then make a decision - and stand over it.
Protect the team. You are the umbrella that shields the team from all the external goings on. The project managers, product owners, customers, sales and support. Distil their input down to what the team need to know and communicate this, keep the team informed and you'll be letting the team get on with their job.
Don't be afraid to change things If something isn't working don't be afraid to change how you do things. Don't change everything at once or you won't know which changes are having the biggest impact. Equally, don't be afraid to change things back . Observe and adapt - admit when something is not working and roll it back. This can be used to your advantage when implementing changes the team might be resistant towards. Introducing alterations on the basis of "let's try this for 2 sprints and see if it helps us... we can always change back later" can help overcome that reluctance since the team know the process will be revised should the changes prove ineffective.
Feel a certain duty of care to your team's careers: If you have a good team you want to keep them together as long as possible. In my experience, people don't just change jobs for a higher salary - often they want a new challenge, to gain exposure to new technologies, or try things like project management or business analysis say. Talk to them, figure out what they want from their career and try to put those opportunities their way. (But know there is only so much you can do for them - they need to be the main person looking after their career. Don't give somebody an opportunity, no matter how badly they want it, if they haven't shown they have half a chance of doing a decent job at it).
Finally, your questions around scrum ceremonies and dealing with a PO is quite broad in nature and this is already a lengthy answer. However, If you have specific questions I'd be delighted to help you out..
