甘い and 甘くare both 形容詞　（adjective) For example, you can say like below, これは　甘いぶどうです　 私のケーキは　甘いです When you use the word 甘く, we usually add ない　(not) or て( means and) これは　甘くないぶどうです 私のケーキは　甘くておいしいです

HI My name is Sgt Tyler Williams, and a citizen of the United State of America, i will brief you more once i hear from you as soon as possible i will like to discuss with you, but not here in italki email me to ([email protected]) With Regards Tyler Williams

Ah thank you

甘い：adjective 甘く: adverb i.e) 甘くする make it sweet