Doubt on lightning channel opening It's 5 days since I opened my first (and unique, for now) lightning channel.
Unfortunately it seems that only me have funded the channel while the counterparty didn't, so the channel it's actually a unidirectional channel.
Indeed the output of the command lightning-cli listchannelsshows direction: 1 (I'm running the c-lightning implementation). 
Is it normal that the counterparty doesn't have funded the channel yet after 5 days or I should think I've misconfigured my channel?
Channel funding (and the distribution of funds) is determined at the time of channel opening. Once opened, a party cannot ‘add funds’ to the channel, this would require opening a new channel. 

If you opened the channel and did not specify that some number of sats should be pushed to the remote node at the time of opening, then the channel will open with the entirety of the balance on your side. Note that pushing sats to the remote node is equivalent to making a payment to the remote node. 

If you send a payment using the channel you opened, you will gain an ~equivalent amount of incoming capacity.  

The current BOLT spec does not include multi-party funding, but this feature is planned for future updates to the spec.