I thought working as a server would be fun but I guess it isn't.
「ウェイトレス」は server や waiting staff と言います。
先生:I hated the job I did for six years.
私:What kind of job did you do?
先生:I was a server.
私:Being a server seems like a fun job.
「ウェイトレスの仕事って楽しそうだけど。」
1) Being a server seems like a fun job.
「〜そうだけど」は seems like ~ を使って表現できます。
2) I thought working as a server would be fun but I guess wasn't.
「〜そうだけど、そうじゃないんだ」は ... would be fun, but I guess it isn't などとも表現できます。
ご参考になれば幸いです!