bios:206: [string "xxxx"]:4: '=' expected

Need helpf with this

while not redstone.getInput("left") do
redstone.setOutput("back",right)
term.clear()
print("Keller oeffnen oder schliessen?")
print("open/close")
a = io.read ()
if a == "open" then
print("Passwort eigeben!")
b = io.read()
if b == "killer" then
redstone.setOutput("back",false)
else
if a == "close" then
print("Passwort eigeben!")
c = io.read()
if c == "killer" then
redstone.setOutput("back",right)
else
print("Falsche eingabe!")
end

bios:206: [string "xxxx"]:4: '=' expected

I have noted the corrections in your code. If something doesn't make sense ask and i will try to clarify it

Spoiler

while not redstone.getInput("left") do
    redstone.setOutput("back",true) -- you ues true meaning on or false meaning off
    term.clear()
    print("Keller oeffnen oder schliessen?")
    print("open/close")
    a = io.read ()
    if a == "open" then
	    print("Passwort eigeben!")
	    b = io.read()
	    if b == "killer" then
		    redstone.setOutput("back",false)
	    else
		    if a == "close" then
			    print("Passwort eigeben!")
			    c = io.read()
			    if c == "killer" then
				    redstone.setOutput("back",false) -- same here
			    else
				    print("Falsche eingabe!")
			    end
		    end --  you messed a few ends eatch IF needs a END
	    end
    end
end

Close the condition "if" and fix the second line.

while not redstone.getInput("left") do
redstone.setOutput("back", true)
term.clear()
print("Keller oeffnen oder schliessen?")
print("open/close")
a = io.read ()
if a == "open" then
print("Passwort eigeben!")
b = io.read()
if b == "killer" then
redstone.setOutput("back",false)
else
if a == "close" then
print("Passwort eigeben!")
c = io.read()
if c == "killer" then
redstone.setOutput("back",right)
else
print("Falsche eingabe!")
end
end
end
end
end

the problem is the second line there:


redstone.setOutput("back",right)
should be

redstone.setOutput("back",true)
redstone.setOutput("right",true)

lol, double ninja'd :)/>/>

Ok accepted now the code look like

while not redstone.getInput("left") do
redstone.setOutput("back", true)
term.clear()
print("Keller oeffnen oder schliessen?")
print("open/close")
a = io.read ()
if a == "open" then
print("Passwort eigeben!")
b = io.read()
if b == "killer" then
redstone.setOutput("back",false)
else
if a == "close" then
print("Passwort eigeben!")
c = io.read()
if c == "killer" then
redstone.setOutput("back",true)
else
print("Falsche eingabe!")
end
end
end
end
end

and the same error

This code has been tested and works. If it fails for you there is something wrong with your Computer craft in game computer or your computer craft Install.

redstone.setOutput("back", true)
while not redstone.getInput("left") do
	print("Keller oeffnen oder schliessen?")
	print("open/close")
	a = io.read()
	if a == "open" then
		print("Passwort eigeben!")
        b = io.read()
		if b == "killer" then
			redstone.setOutput("back",false)
		end
	elseif a == "close" then
		print("Passwort eigeben!")
        c = io.read()
		if c == "killer" then
			redstone.setOutput("back",true)
		else
			print("Falsche eingabe!")
		end
	end
end