You have changed your Blogger Layout from untrusted site which has interesting layout, but now you lost the comment box beneath of the post.
Here is the solution how to fix it.
Your order is change the comment configuration:
Go to 'Settings' and set the tab to 'Comments', there you'll see 'Comment Form Placement', mark it to be 'Embedded Below Post'.
Now, go to your Blogger Dashboard, click 'Layout' and set tab to 'Edit HTML', do not forget to save your template first before do the tutorial section above.
2. Your order is to find these code inside your layout HTML:
<p class='comment-footer'>
<a expr:href='data:post.addCommentUrl' expr:onclick='data:post.addCommentOnclick'>
<data:postCommentMsg/></a>
</p>
</b:if>
Notes: To shorter your time to find those code, just simply hit CTRL+F to open the 'Find' feature from your internet browser, find <p class='comment-footer'>, but be careful because there are two similar or same codes. Just find <p class='comment-footer'> which has <a expr:href='data:post.addCommentUrl' expr:onclick='data:post.addCommentOnclick'> code below its code.
Replace those code with these:
<p class='comment-footer'>
<b:if cond='data:post.embedCommentForm'>
<b:include data='post' name='comment-form'/>
<b:else/> <b:if cond='data:post.allowComments'>
<a expr:href='data:post.addCommentUrl' expr:onclick='data:post.addCommentOnclick'>
<data:postCommentMsg/></a>
</b:if> </b:if> </p> </b:if>
Now save your layout and see whether it is changed or not.