What should I do?
I will receive around US$4000 next year.
Should I spend it on a more expensive guitar or on guitar courses?
Here is the course I am interested in, which teaches worship guitar. I can learn from BGR to SWD with my money. It is a group guitar course. But then, maybe justinguitar.com and online guitar course is enough for my need, and the money is better spent on geting a better guitar, one that has better sound.
A better sound comes from your fingers, not a more expensive instrument.
Generally, you should wait until you reach a certain level before spending a lot of money on an instrument. Among other considerations, guitar isn't for everyone and you may find it's not for you, or there are other instruments you'd rather play. Time will tell.
How has it been?
Have your bought your guitar?
Have you started any lesson?
Are you able to play guitar now?