Showing code while navigating post or other option from admin dashboard.

When i am trying to edit a post or going in plugin page from admin dashboard or other page, it redirect me/ shows me code. I thing its html code.

I scroll down to that page and saw that there is
</body>
</html>
0

I understand these are closing tags for html. Then i checked for opening tag but there was none. It start with pics</div><div class="sticky"></div><div class="post_format"></div></div><div class="row-actions"><span class='edit'> which i don’t understand.

Please help me. I am totally frustrated.