Translation:Any bed is better than not having a bed.
I am going to analyze this sentence but please keep in mind I am learning here too. I checked and "mejor que" is a compound preposition. When we have two verbs (first one conjugated [ser] and second one infinitive [tener]) referring to the same subject [cama] we generally need a preposition between. Normally the prepositions are 'a' or 'de' (There are exceptions verbs like poder where none are needed as you've seen in this module). The infinitive can be 'to have' or it can be 'having' depending on context. Hope it helps.
One can certainly express the idea adequately without the "at all".
As the "at all" is an optional emphasis of the expression "no bed", perhaps there is an equivalent emphasis that could be likewise present in the Spanish, but is not. An equivalent to "nunca" versus "jamás".
After tener, if you are just saying something like "I have a car" "I have a bed" you just use tener and the noun.
The only time you use a number like un/una is if you are specifying that you have ONE of those things.
I have a car = tengo coche
I have one car = tengo un coche
I put, "Any bed is better than to have no bed." That is not they way I would say it in English, but it conforms with the sentence given. DL does not agree. This is a case where there are a lot of subtle variations in English that are correct but not included in DL's approved list. Adios, corazon!
If I translate every word as such I get: "Whatever bed is better than to have no bed." Editing that translation I arrive at: "Any bed is better than not to have a bed." Looking at the fact, that in English a construction with "-ing" is used very frequently, I chose to translate "tener" as "having" >> Any bed is better than not having a bed.
I translated it as "Any bed is better to have than no bed." I don't see how that could possibly be wrong. It means essentially the same thing as "Any bed is better than not having a bed." And, after all, I translated! Word order isn't supposed to matter in translations, only meaning.