I have a current Schengen visa but it is going to expire halfway through my next trip. Can I still travel on it or just get it extended?
No. You must leave the Schengen states on the last day that the visa is valid and that date can not be extended. You will be required to make a new application for any future trips that fall outside the visa validity. Also, you are not permitted to hold 2 current Schengen visas at the same time so you will either have to- a-wait until the current visa expires and then re-apply or b-get the current visa cancelled by the issuing embassy and then re-apply.