Sorry to be that guy, but you’re heading into a steep learning curve and time sink if you’re new to game programming (you should at least have a rather strong programming/java background, so good knowledge about OOP, Java Interfaces, floating points (e.g. why equals checks fail pretty often)) AND Art, you have much work to do.
First and Foremost: To achieve any “good” quality, you need a team of multiple people and/or a shitload of money.
Your picture looks like a multiplayer game, if so, that’ll throw you back 1-2 years, since this influences the structure of the game, you handle all kinds of problems like lag and desync.
The only advantage Unity/Unreal have is that you can download everything. Player Models (assets), skies, even Multiplayer is somewhat built in, many premade things like UIs, Post Effects etc. For JME you have to do them your own, get open source libs and/or get the assets from somewhere and convert them.
So if you are completely new, start with something really simple like walking around on a plane surface, jumping etc. Then you could add stuff like doors which open when you are in proximity (there you can make the door animated, so you can teach yourself how to do simple animations in blender) [Note: Usually you would not animate doors unless they perform complex motions].
Anyway it’ll take you multiple years until you have something to be proud of, but if you don’t mind, you’ll enjoy that adventure.
And yeah, try blender tutorials on youtube, but alone the models may take multiple years (and they have their own dependencies like textures. Buy or DIY).