"Es ist meist größer."
Übersetzung:It is usually bigger.
"It is mostly bigger" isnt incorrect. However 'mostly' would generally refer to its size whereas 'usually' is a reference to a temporal condition - Coming to a narrow crossing of a river someone may comment, " It is mostly bigger" referring to the rest of the river. If coming to the same narrow crossing during an unusual dry season and finding the crossing even smaller the comment would be better voiced as, "It is usually bigger!" making reference to the normal condition of the river at other times.
now in german please, i am currently not available to understand it. and if you want i will correct you.
That would sound awkward to a native speaker. Usually has the connotation that at one point it was a larger size than it is presently
Das frage ich mich auch. Wäre nett, wenn das jemand erläutern würde. Usually aber nicht mostly..
it usually is bigger - sollte doch auch stimmen!!! da liegt halt die Betonung auf "meist"