Bedre ta være på denne..
Jepp. Bedre å ta vare på denne. Or: Ta bedre vare på denne.
Vare (in this context, taking care, be careful) is an uncountable noun with no other forms.
hvor man snakker norsk
Why is not accepted "I need an another planet"? Is it a wrong translation?
The indefinite article "an", is already baked into the word "another", so you don't need to add it a second time. The rest of your sentence is correct.
. . . says the astronaut.
Doesn't it mean a different planet?