Mayur vekariya

maybe your role for a user not as a Admin.If you have many user in your blog then check login using other id which have all access permission and change your role as admin.

In your post image size may by too much larger.that cant set as a featured image so you have to set manually for that post.

for set featured image for individual post check this: https://www.screenr.com/q7c

Yes in style.css file.

#top {
border-top: 2px solid #e6e6e6;
border-bottom: 2px solid #e6e6e6;
height: 33px;
line-height: 33px;}

Change the height.

No there is separate options for set a featured image.
You have to set there image by size 50×50,150×150 whatever your requirement.

If you did not set the featured image then it will take automatically from post.but,here is problem comes if image size is not appropriate for the featured image then it will not show.

you have to set relevant sized image for better feature image display.

check out this plugin “Auto Post Thumbnail”.

Your top area is smaller than your logo’s height.
You do one thing change the top area’s height and check it.

did you set featured image while post?

Go to the themes CSS file you will find wrapper size like,

#wrapper {
background:#fff;
margin: 0 auto 15px auto;
padding: 10px 15px 0 15px;
width: 1000px; }

change the Width of wrapper as per your requirement and save and check.