I Find a Bug in Minecraft

I dont need Enivroment cause its a Bug in Minecraft.
I got into a world thats just the normal generator. I called it Adventure Map.
The Seed of the World is: 199823429691528808
And heres the Error:
Changing view distance to 16, from 10
[17:01:39] [Server thread/INFO]: martinamama[local:E:75b4e792] logged in with entity id 55924 at (-3.1151813979439043, 64.06027311411448, 73.3862983984886)
[17:01:39] [Server thread/INFO]: martinamama hat das Spiel betreten
[17:02:02] [Server thread/WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 23855ms behind, skipping 477 tick(s)
[17:02:17] [Server thread/WARN]: Can't keep up! Did the system time change, or is the server overloaded? Running 14429ms behind, skipping 288 tick(s)
[17:02:23] [Server thread/INFO]: Saving and pausing game...
[17:02:23] [Server thread/INFO]: Saving chunks for level 'Adventure Map'/Overworld
[17:02:32] [Server thread/INFO]: Saving chunks for level 'Adventure Map'/Nether
[17:02:32] [Server thread/INFO]: Saving chunks for level 'Adventure Map'/The End
[17:04:31] [Server thread/ERROR]: Encountered an unexpected exception
java.lang.OutOfMemoryError: Java heap space
[17:04:38] [Server thread/INFO]: Stopping server
[17:04:38] [Server thread/INFO]: Saving players
[17:04:45] [Server thread/ERROR]: Exception stopping the server
java.lang.OutOfMemoryError: Java heap space
Exception in thread "Server thread" java.lang.OutOfMemoryError: Java heap space

When i had a seeing of 10 Chunks its all fine but when i do 16 Chunks a region is blinking with i dont know with Chunks that are changing themself from bedrock to Bioms to... In the screenshot you can see it(I Promise nothing with Photo Shop 🙂 ). It was lagging very much but i did a Video about it,too .Its rendering now and i will answer my question with the link to my video its in German but i wrote something in English, too.