There aren't any German words that start with the letter y.
Yes, the first letter of days and months has to be capitalized Every noun has starts with a capital letter in German.
A question like this takes a long time to answer. I have added a link below that will take you to a German dictionary. There you can take your pick, just type a letter into the box in the top right corner without clicking any thing a small pane opens with several examples from which you can chose.
Some adverbs that start with A are:actuallyawfullyangrilyanxiouslyabsolutelyaccidentallySome adjectives that start with A are:aridangelicawfulangryanxiousable
German children start school at the age of 6. The school day starts at 8am
start
Neighborly is a positive adjective. Neat is a positive adjective.
No German adjectives start with X
irksome
Agreeable is a positive attitude. It begins with the letter a.
apprehensiveantagonisticantediluviananticlericalanticipatoryantitheticalappreciativeapprehensivearistocraticastronomicalasymptomaticattributableaugmentativeawe-inspiring
No
violent
Zealous is a positive word. It starts with the letter z.
jarred or jerked
scholastic
openhearted
ripe, rude