Screen cracked; replace the old screen with new screen

@vijay34978 since iFixit does not yet have a specific guide for this, use something like this video to replace the LCD. Replacements are widely available at many online stores. Select one within your geographic region.

As for better waterproofing, that is pretty unlikely. You will need to reparable the sealant etc. So, anytime you have a repair on a device like this, consider waterproofing less efficient as it was from the factory.

While you work on your phone, take lots of pictures. Once you are done with it, take those pictures and create a guide for iFixit. That will help the next person that has a device with the same issues as you do. It's easy and fun to create these guides. https://ifixit.com/Guide/new The iFixit community will appreciate this.

Repair is War on Entropy!