How do I optimize size of my unity word puzzle game?

Try to resize the Tetxure resolution, but i think that you wont get the size much smaller. In my current Project the size of the Assembly C#.dll ( the game code) is 3MB and 1 texture sometimes have 80mb. So its difficult to get it much smaller! You can also try to lover the Quality at a Audio Import settings.

resize all your sprites with power of two values. (maybe creating logical atlases could help more) this way Unity can compress your visuals better.

also if you dont mind leaving some devices not supported for your game you can decrease supported api level count in build settings.

you can change your audio files from stereo to mono channel.

etc.

You should always start by reading the manual: https://docs.unity3d.com/Manual/ReducingFilesize.html