When i started planet coaster and started sandbox mode i closed the game a lot of times instantly, because i just had no idea how to start and what to do. So many beatiful parks on reddit and youtube and im sitting here with a lot of time and motivated - but just with no idea what to build and how to build...
Well, i get the same feelings when i start a new zoo at PZ, but i dont quit anymore xD
First thing ist to accept that your first buildings will never be as good as the ones you see on youtube, made by players with hundreds of hours of playtime. When its about learning how to build, i recommend you to use a blueprint and start editing it. Take this building and start to edit it, maybe its getting not that beatiful, but just dont care. Youre building mate. And the more you do this, the more youll learn. And soon you will start building your own simple buildings with the tools and skills you just got by editing the the blueprints in your way.
Wont take long and youve built your first own buildings and the more experience you get, the better you will get and yout skills gonna increase. Like with everything in life: learning by doing.
When its about you dont know what to build, so search through the internet for some ideas or just start doing some random stuff. For me a lot of ideas are coming whilr building. Im buildinh for half an hour and suddenly i get an idea and think "well, lets delete this and this and i gonna do it new in a better way!". I really like to relate the pathing system into my buildings (but thats not that easy at the start. Path-system will make you crazy sometimes when youve build for some time. Its very sensitive...)
I mean, just DO something and dont be mad, your buildings aint as good as of other players with a lot more experience. The more you build the better your results will be. Promise!