I tried to compile my apk, and then show that, somebody help me

Somebody know hot to solve it, its for a high school project:

App Inventor is unable to compile this project. 
The compiler error output was 

________Preparing application icon
________Creating animation xml
________Determining permissions
________Generating manifest file
________Attaching native libraries
________Copying native libraries
________Attaching component assets
________Compiling source files
(compiling appinventor/ai_jijadan/Lego/Screen1.yail to appinventor.ai_jijadan.Lego.Screen1)

ERROR: appinventor/ai_jijadan/Lego/Screen1.yail line 234: duplicate declaration of 'Nxt'

ERROR: appinventor/ai_jijadan/Lego/Screen1.yail line 209: (this is the previous declaration of 'Nxt')

Kawa compile time: 1.689 seconds

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You have coding errors in your blocks.  In the Blocks editor, look in the lower left corner of the window for the yellow and red triangle icons. If the red icon has a value larger than 0, you have a serious coding error.  Find the block in your code that has a red triangle and fix it.   Red triangles always inhibit creating an apk or running a project in the emulator or possibly creating an aia file.     Yellow triangles are more forgiving, however, sometimes, these need to be fixed because they trip an internal warning and not billing puzzle piece sockets are left un-filled.

Somewhere in your Lego NXT commands, you are either calling a Nxt incorrectly or the app calls it twice.  Without seeing a screen capture of your blocks, we can only guess.  Find the error, change some blocks (or temporarily disable any of your Nxt command blocks to see which is causing the problem) and try to compile again.    The DoIt AI2 debugger might also be your friend.

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