Since you said friends and loved ones, I would never use the formal versions of the Japanese greetings Giles mentioned below, and rarely his informal versions.
For morning greeting, I’d either say おは (oha) [ohayo shortened], よー!(yo!) [really hey! or what’s up!], or less frequently おっす (ossu…but without aspirating the u at the end). You can even say ヤーホー! (yaho!) but be careful as this is typically used by young girls.
There are many ways friends and family members convey good night, or take care, or see ya. For ‘until tomorrow’ which is また明日 (mata ashita), I would simply say 明日 (ashita) [pronounced: a-shta. The ‘I’ is silent] For ‘see ya’, or ‘talk to you soon’ I would say either またね (mata ne), またなー (mata naa), じゃーね (jyaa ne), or じゃーなー (jyaa naa), sometimes simply じゃ (jya), or even それじゃ (sorejya).
じゃーまたね (jyaa mata ne) pushes the formality a bit too much for me, especially with close friends.
Saying おやすみ (oyasumi), and definitely おやすみなさい (oyasumi nasai), feels like I am saying “I’m going to bed now”, which may not be what you want to convey. In fact, it has been a very long time since I have heard anyone in real life say the full おやすみなさい (oyasumi nasai), although I am sure many still do.
Another very informal way to say ‘talk to you soon’ in Japanese, especially when texting or speaking on the phone is : よろしく (yoroshiku) [pronounced “yo-ro-shku”…the ‘I’ is silent], which is kind of like “Thanks, see ya.” Although yoroshiku has become kind of a catch-all to mean a number of things depending on context, saying it, especially when texting or speaking on the phone conveys ‘this is the end of our pleasant conversation.’
I was amazed to find out (as I went to check so no one would criticise my spelling) that for such a precise language, where there is a significant movement against people spelling compound words as separate ones, god morgon/god natt and godmorgon/godnatt are accepted spellings.
Dutch:
Good morning: goeie morgen, or “morgen” (both colloquial)
Good night: goede nacht. (For some reason the more colloquial “goeie” doesn’t seem right at night to me.
Sleep well:slaap lekker
Afrikaans
Good morning: goeie more
Good night: goeie nag
Sleep well: lekker slaap
Yiddish
Good morning: a gutn morgn
Good night : Gute naght
Sleep well: shlohf’ gezunt