I Need Help Please

so, whenever I try to play minecraft, it says the messege: Could not reserve enough space for 1331200KB object heap

so on the "JVM arguments" I placed less ram. but after playing a bit, the blocks just dissapeared and reappeared rapidly

Do any of you guys know what can I do to solve this problem?

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bump

 

Place more RAM, not less. Minecraft is running out RAM

 

but when I place less, it lets me play, if I put more I get the message

 

You need the less RAM amount. That flashing block bug is common, and is unrelated. That bug usually occurs when your render distance is too high on a complex map. Try setting your render distance down as well, but not immediately. You should slowly put down your render distance, about 1 or 2 at a time, otherwise it could get worse. Then it should be OK