What can I do to extend my vocal range to sing higher and stronger notes?

I can sing well but I find it difficult to hit high notes. The more high I go my voice gets faint and I need to strain to reach some notes. What do u suggest I do?

There's nothing better than semi-occluded exercises like singing through a straw to help with range extension! Here's a quick intro and how-to: https://youtu.be/EecSsVgM3TM.