Climb a tall and beautiful mountain. 爬 (pá) - to climb 又高又美 (yòu gāo yòu měi) - tall and beautiful 山 (shān) - mountain

in English you can say "my apple is red and sweet" that is "and" is used to unite adjectives so in Chinese 又 to unite adjectives 爬 又 高 又 美的 山 = climb tall and beautiful mountains

爬又高又美的山 == 爬美丽的高山。 climb a beautiful high mountain。 klimmen een mooie hoge berg. 又高又美的山 is a little strange to Chinese people，although it is correct。