Leaf status means that you're connecting to other hosts (called ultrapeers) who handle most of the search traffic & shield leafs (typically people who are firewalled or who have slower connections) from unnecessary traffic

If you're firewalled, you'll always connect as a leaf.

There's more info below.
GnuFU en - Gnufu
User Guide Connections - LimeWire

Can you give us your system details? Then we can try to help with your firewall issue & maybe your download issues as well. The link here shows which details we need: System details - help us to help you -> Provide these details when you post!!!