I cannot build a draw bridge/gate to protect my castle...?
Kind regards,
sacha70

Check the reasons why in the build window (the numbers next to the building you are trying to build)
If there are any enemy troops within 6 hexes you will need to destroy them before you can build there. This was increased from 4 to 6 recently.

Thanks for the reply. But it's not in my build window. That's the problem. I can build stone walls, etc... But no drawbridges...
And I can't find an upgrade or so related to this...

The answer is in the online manual.
Look in Buildings > Medieval
At the bottom you'll find Drawbridges
This gives its requirements:
Building : Blacksmith
Tech : Drawbridges

Lookup Techs > Medieval
Under blacksmith:
"Drawbridges

Requirements
Tech : Castle Defense
Building : Military Academy"

Castle Defence in turn require Tech: Castle Protection.
Military Academy requires Tech: Military

So, to build your first drawbridge, you need to have bought the following first:
+1500 Building: Blacksmith
+2000 Tech: Military
+1500 Building: Military Academy
+3000 Tech: Castle Protection
+3000 Tech: Castle Defence
+4000 Tech: Drawbridges
+ 750 each drawbridge
=====
15750, 4 techs (+ I'm assuming you also spent 2000 on Tech: Building materials to save 750 on these buildings)
You could save yourself the cost of the drawbridge tech and use the money saved to build Military Acadmeies instead - these have half the health and can be taken over by enemy commandeers if you don't keep a unit within 4-6 hexes (not quite sure - I thik this has increased recently)
Towers are another credible candidate - they have more hitpoints and are useful for your defending ranged units.

Thx for the detailed explanation. It's ok now... Probably I had one upgrade too little.
Thx!