Welcome to the Vercel Community! 
Feel free to drop into Introductions to introduce yourself.
This navigation works only for 1 day after that I am not able to navigate. When user click on any case study then it’s redirect the case study main page.
From what I understand, you made no changes to your code (?) and now, the navigation to the case studies is broken. Is that right?
I went onto your website and can confirm that the only case study that works is this one: Case study Telindus | NewU
It’s worth checking how you manage your routes on your app. Feel free to share any snippets here as it’d help us figure out what wrong.