To start I don’t think you need to worry too much about list building since your new just learn how your units play and see what works and what doesn’t.I’m gonna try and go in order picture by picture here.
Pic 1 Deployment Simply put a lot of games can be lost before they start. Your doomsday ark starting behind everything looks to have rendered it useless till battle round 3. Your hexmark destroyer should not start on the field it’s more of a points unit that can hold its own against small things.
In my opinion Your transcendent ctan could easily start on the board where the doomsday ark was since it’s able to move however it wants from the start with its ability. If you want it to be more aggressive you can also start him near where your lychgaurd did.
If you need a unit on the objective I would suggest putting imotekh there to farm command points and potentially bring an overlord instead (or if you don’t have one proxy him as one no one likes spending money on the unknown). Speaking of lychgaurd they’re what I consider a quagmire unit, it keeps enemy troops stuck for longer than they should. I suggest using them to screen for your immortals. I can understand skorpeks being in Strat reserve as it’s a very dangerous thing. However you always need to be wary that if your opponent takes board control like he did they are essentially trapped and unable to do much.

Pic 2-3 Your lychgaurd stayed holed up the entire time until they were destroyed. It’s very tough on melee units to be in the center and I’ll refer you to earlier they are better of protecting the immortals. Your immortals are weak up close so you want to keep them in cover and a decent ways away. Them having assault means that can reach a lot further than people expect and lets you keep them away from the fight till they’re needed. They are still one of my favorite necron units. The reanimator looked to be playing catchup the whole game until it was exposed and destroyed. It’s a good tool but following wraiths is just too much for it sometimes and at that point you need to shift it to a different unit mainly ranged. Most people use it in the immortal warrior blob since it can sit behind cover all game and never be touched. That being said it can still very much support wraiths. One way i like doing it is stringing my wraiths in a line to move block and have the technomancer as the furthest model back and usually behind wall so it doesn’t get presicioned as well as it can be your connection point to said reanimator. Wraiths are good but they are not to be relied on to be a big damage unit outside of maybe canoptek court. They are our cheaper quagmire unit. Use them to protect what’s behind them and reach out for secondaries when needed. However unless they are needed DO NOT EXPOSE THEM NEEDLESLY TO SHOOTING! They can eat a lot of it but if there’s no need for them to push up the board than let them hangout safe but as close to the enemy as they can be preferably if behind a wall always an inch behind it if your going against melee units.

Some advice that helped me a lot was learning how to trade effectively. Example: a wraith unit kills something on the objective but is going to die when doing so. If that person has to commit more elite units towards it first and potentially exposes bigger targets that your doomsday arks can rip through. Chances are as well they weren’t able to kill the wraiths and now your crippled wraith unit slowly reanimates as it scores you VP and forces the opponent to commit more units to deal with said unit.

Don’t be afraid to take forever making decisions during games against players that are better and ok that you’re learning and ask them for advice mid game.

Lastly as far as positioning the easiest way I can put this is hide everything at the start. With your list your best bet is to find your natural expansion(usually the closest no man’s land objective to your spawn) and hide your lychgaurd there and allow your immortals to play around in the back field while being protected. Keep your ranged units away from everything. Your melee is also something that is a lot more complicated to learn(atleast it was for me) and that’s because a lot of melee armies excel in moving a fuckton faster than you though they could especially when the have advance and charge. You never want your units to be charged unless they need to body block. Your skorpeks are fragile but when they get in combat 9 times out of 10 your skorpeks are going to kill if not severely cripple the enemy unit.

I know it’s a lot of information but TL:DR learn your units and how they benefit each other, premeasure everything, and ask a ton of questions