In addition to what MadameCurie posted above.
If you are truly stuck you may have no other choice but to contact Pixel support directly.
Have you tried completely shutting down your game & restarting it..... fully closing down not just swiping it into the background.
Clear your cache, cookies, history, etc.
If you have you player ID number & game progress registered with either your email address or Facebook account.....try uninstalling & reinstalling.
If none of these suggestions work for you....then i suggest that you contact Pixel support directly.
You can contact Pixel support directly through your game settings menu
Alternatively you can contact Pixel support directly via this link
Do not type in the white search box ... go to the categories written in blue.
Remember to check your spam / junk folder for replies.
Do not send multiple Pixel Support tickets in quick succession or their spambot could eat them.
You can check out the relevant Wiki pages, quests, maps, videos, guides, walkthroughs & hidden gifts/bonuses
Personally I find the maps & walkthroughs much easier to consult, study & follow in certain scenarios instead of the videos.