I have this friend I met on online classes, we shared some interest and started talking a lot, every day to exact. The thing is I've noticed that said friend really talks themselves down, they are always saying stuff like "I am so dumb" "I am so stupid" and stuff like that, since we mostly just text I don't know the tone they are saying it but it doesn't seem like they are joking. I don't want my friend to feel this way, I don't know how to respond when they say things like this, I mostly ignore it because I'm scared of saying something wrong :( Also they are always praising me, saying how they think I'm smart and wise and then they add that they are dumb :( I don't want them to feel this way, I wanna help them but I don't know if it is my place, I don't know if they wanna be helped. They reveal to me that they have social anxiety and don't socialize much, I really wanna make things better for them but I'm no therapist. 
I would like to know if you have any advice on how to respond when they are self deprecating and if I should try and help them at all, sometimes I try to fix peoples lives when I just should be minding my own business :/