It seems to be because of the slow speed of the internet. Have you tested the speed of your internet? If not, you should do it now. And for this I would recommend this site ptcl speedput. Make sure that you are getting the actual speed of the internet. There can be a number of reasons behind this problem. Also, check out your router if you are using an old router. You can also set up a wifi booster at your place to give strength to the internet signals by increasing the coverage area.