Learn Arabic (Modern Standard): بعض المعلومات في التحديث قديمة.

بعض (some) forms an Idafa (possession) relationship with the word after it. A major rule of Idafa is that the first word never takes ال (the). Therefore, we just use بعض followed by the defined word المعلومات.

Since المعلومات has ال (the), does this literally mean 'some of the information'?

Yes! While we say 'some information' in English to sound natural, the Arabic phrasing is literally 'some of the information'. It refers specifically to the information in this particular update.

Why is the adjective قديمة (old) feminine singular when المعلومات (information) is plural?

In Arabic, plurals for non-human things (like information, books, or cars) are always treated as feminine singular. So, the adjective describing them must be in the feminine singular form, which is why قديمة ends with a taa marbuta.

Where is the word for 'is' in this sentence?

Arabic doesn't use a word for 'is' in present-tense sentences. You just put the subject (بعض المعلومات في التحديث) and the description (قديمة) next to each other, and the 'is' is automatically understood.