Here, input("Age") returns a value (which you probably meant to assign to the age variable), and therefore you are trying to assign two values to one variable (18 and the result of input("Age")), so that will not work. You probably want this:
age = input("Enter your age")
Now let us look at your if block:
Here you assign the variable message to the string "not old enough" and then immediately re-assign it to a new value " try again later" throwing away the first part. Perhaps you meant to concatenate the strings, but that is highly unnecessary since you can just write the whole thing as one assignment. That being said, it looks like you probably wanted to print it out which means you do not need any variables and can just print out the statement directly like this:
if age <= 17:
print("not old enough, try again later")
The last part looks fine, so putting that all together it would look like this:
age = input("Enter your age")
if age <= 17:
print("not old enough, try again later"
elif age >= 35:
print("too old to play")
As a total aside, telling someone who is under 17 to “try again later” is a bit of an unusual way to phrase “wait until you turn 18” (since that may be years from when they see that message) and telling gamers who are over 35 they are too old sounds pretty rude and unnecessary. Not to mention the fact that you asked for the age input so the information is unreliable. I am sincerely hoping this is for some class assignment rather than a real project.