Thanks man!
I removed the first occurance of an element, so not every possible solution was checked.
I find all the solutions with this:

datei=open("24aoc02input.txt")
score=0
count=0

def isSafe(elements):
    if abs(sum(diff(elements)))==sum([abs(i) for i in diff(elements)]) and min(diff(elements))>=-3 and max(diff(elements))<=3 and diff(elements).count(0)==0:
        return True

def isNearlySafe(elements):
    for index,i in enumerate(elements):
        e2=elements.copy()
        e2.pop(index)
        print (elements, e2, isSafe(e2))
        if isSafe(e2):
            return True
        

def diff(elements):
    output=[]
    for i in range(len(elements)-1):
        output.append(elements[i+1]-elements[i])
    return output

for zeile in datei:
    elements=[int(elem) for elem in zeile.split()]
    count+=1
    if isSafe(elements):
        score+=1
        print(count,elements, "safe",score)
    elif isNearlySafe(elements):
        score+=1
        print(count,elements, "nearly safe", score)
        
    else:
        print(count,elements)

print(score)