I am technology challenged.

My S6 Active has been running really slow. I pretty much deleted pics and most apps. I had more apps on my Note 3 and it ran better. I really don't want to do a factory reset because I don't want to lose text messages that I have on there. I see a lot of apps that came on the phone that I have no clue what it is for. When I go to delete or disable them, I get a warning about the phone possibly not running without them....or something to that effect. What pre-installed apps can I delete or disable and not worry? Hope I am explaining myself right. This stuff confuses me.