how to redirect only the posts from my old domain

Question

Please tell me how to redirect only the posts (not the categories and not the homepage) of my old domain to the new domain.

i have tried everything i can (in .htacess) like this: first thing i tried

or this:

    RewriteCond %{HTTP_HOST} ^(www\.)?olddomain\.bg$ [NC]
#RewriteCond %{REQUEST_URI} !\.(jpe?g|png|gif|ico)$ [NC]
RewriteCond %{REQUEST_URI} !wp-admin
RewriteRule ^(.*)$ http://newdomain.bg/$1 [L,R=301]

Please please help me. Thank you

Edit: i did try this:

RewriteRule (.+) http://www.newdomain.bg/$1 [R=301,L]

But it redirects all but the homepage. I need to exclude the categories pages too(10 categories) ? How to exclude other pages from this rule?