Learn Polish: Ona systematycznie porównuje dane w systemie. - She systematically compares the data in the system.

The infinitive is porównywać (to compare, imperfective), which is formed from the perfective verb porównać by adding the -ywać suffix. A crucial rule is that verbs ending in -ywać drop that ending and use the -uj- stem in the present tense. That is why it conjugates as porównuje (she compares) rather than keeping the "yw" spelling.

Is dane (data) a regular noun? It seems to have an adjective ending.

It functions as a noun, but it declines exactly like an adjective! The word dane literally translates to "given things" (derived from dać, to give). Because of its origins as a participle, it takes plural, non-masculine-personal adjective endings. In this sentence, it is in the accusative case as the direct object.

Why does the word system change to systemie in this sentence?

The preposition w (in) requires the locative case because it answers the question "where?". For masculine inanimate nouns like system, the locative ending is typically -ie. This ending forces the preceding consonant to soften, which is why the letter "m" is followed by an "i" to represent the soft sound in systemie.

Could the adverb systematycznie be placed at the very end of the sentence?