[19w02a~19w04b] Getting in to nether portal, the game keeps showing me "loading Terrain"

when i created the first nether portal and got into it, i couldn't get into the world and i was forced to shut the game. and when i returned to the game, there was two portal on the overworld. the original portal and the extra portal that is unknown why it is created on there. and since then, the bug that has shown me an infinity loading screen("loading terrain") has almost appeared to me every time i got into a nether portal. i guessed that the extra portal made the bug, so i removed it. and for a while, the bug seemed not appearing to me, and boom! it has appeared to me! then Guessing that the ram in my computer is so small that it can't make the room for loading nether. i exit the world, returned to the world, and get into the nether portal. and again, it didn't seem that the bug appeared to me for a while... and boom. it has appeared to me again. now i'm tired of dealing with this bug alone and for the last chance to make me do this game more, i post about the bug here that has been suffering me.

p.s i'll link my map file to the google drive

https://drive.google.com/drive/folders/1dFUOaSsjqkPrmnhr9_QuO6E7rCmC6_ze?usp=sharing