Need help for changing the text

m not so good at html but i can understand it a bit. so i tried editing my theme. at first it was working but recently when i tried using the other font it did not work even though i edited in the same place where i did before. can someone help me in solving the problem. This is my site https://hipromtech.com/ . i want to change the font of the posts as well as the font titles. Also the color of the font title.