"Animals are welcome in the restaurant."
Translation:Tiere sind im Restaurant willkommen.
I'd say thats the most similar construction to the english grammar.
(part1 of the predicate) sind
(adverb construction) im Restaurant
(part 2 of the predicate) willkommen.
Predicates with multiple parts have the tendency to place one part at the end.
Tiere sind im Restaurant willkommen. Most neutral way to say this, puts slightly more emphasis on the subject.
Im Restaurant sind Tiere willkommen. Also very common, puts the emphasis on the im Restaurant.
Willkommen sind Tiere im Restaurant. Uncommon, puts the emphasis on the Willkommen.
Tiere sind willkommen im Restaurant. Uncommon, somehow "splits" the sentence and puts an emphasis on "Tiere sind willkommen" the location described by the adverb moves more into the background.
You can say:
Tiere sind willkommen im Restaurant. Tiere sind im Restaurant willkommen. Im Restaurant sind Tiere willkommen.
I don't know if Duo accepts all of them, but they are all proper German. You have a lot of freedom as to how you rearrange the sentence as long as all nouns are in their propper case, and your conjugated verb is in second position.
You'd preferably put "Tiere" in front because that's what you want to catch the reader's attention with, it's the main topic the sentence focuses on/stresses, e.g. in a "list" such as this: "Our restaurant can seat up to 200. We have ample parking space available. Tiere sind im Restaurant willkommen."
im is a contraction of in dem.
dem is the dative case of the definite article for masculine and neuter nouns.
den is the accusative case of the definite article for masculine nouns.
in is one of the two-way prepositions that can take either the dative or the accusative case, and that uses the dative case to indicate a location, the accusative case to indicate the destination of motion.
So roughly, im is "in the" while in den is "into the".
For example, ich gehe im Garten is "I walk in the garden" (you walk round and round while you are in the garden) while ich gehe in den Garten is "I walk into the garden" (you start somewhere else and then walk and end up in the garden).