The two glaring problems are pictures and mail.
You can move your photo library to an external drive. There are plenty of online tutorials on how to do this safely, so use your favorite search engine and seek out these articles.
I don't know what sort of mail messages you are storing but for sure, I do not have 37 GB of messages. Heck, I'd be surprised if I had 500 megabytes of messages between the IMAP server and my local mail folders.
The easiest way to deal with this is to go into your mail folders, sort by message size and see if there are candidate messages to delete. My guess is that 20% of your messages are using up 80% of those 37 GB, maybe someone mailed you a massive presentation document, video files, whatever. Start with your Sent Items folder and see if any of those can be removed, then empty mail trash.
Note that IMAP mail is stored locally on your Mac as well as your mail provider's servers.
This is the same with Dropbox; local copies of files are synced with Dropbox's cloud servers. At some point, you will probably want to look at your Dropbox contents and see if any of them are candidates to be moved to your local external disk drive.
But focus on mail and pictures, those two total 78 GB.
Best of luck.