Unfortunately, your haiku doesn't follow the rules of haiku. I'm not good at haiku, but I know some rules. Before explaining, I present a famous haiku.
「古池や 蛙飛びこむ 水の音」 by松尾 芭蕉(Matsuo Bashou)
(ふるいけや かわずとびこむ みずのおと)
Old pond frog jumps the sound of water
→The ancient pond / A frog leaps in / The sound of the water. (Transrated by Donald Keene)
【Basic 2 Rules】
①Haiku needs one "season word(季語: kigo)" in one sentence.
In this example, the "season word" is 蛙(かわず). The frog appears in spring in Japan, so 蛙 is a spring's season word.
By the way, 月 is a autumn's season word. Because the moon gets beautiful in autumn. The air of autumn is clear. It depends on Japanese climate.
②Haiku has 17 sounds in hiragana. (5+7+5=17)
Your haiku in hiragana,
「寒い夕方冬の月を見るや 一緒に太陽」
さむいゆうがた ふゆのつきを みるや いっしょに たいよう (25 sounds)
There are too many sounds...
I think that the first rules is difficult. Therefore, I recommend making haiku within 17 sounds. The second rule is easier than first one.
Good luck!!