For "How have you been recently?"
Formally, "Bagaimanakah keadaan anda kebelakangan ini?"
Colloquially, "Apa cer?" ("Cer" is a short-form for "cerita" ((story)) ) or "Amacam bro?" ("Amacam" is a short-form for "Apa macam" ((Which formally translate to "Bagaimana")) and "bro" is Brother)
For "What are you doing this weekend?"
Formally, "Kamu buat apa pada hujung minggu ini?"
Colloquially, "Apa cer hujung minggu?" or "Hujung minggu ni apa macam (or "amacam") bro?"
The colloquial terms that I provide you with were usually used by "belia" or "orang muda" or youth, but the usage of this term expands to the 30s and 40s age group. Hopefully by practicing this colloquial terms, you can converse better and make people bedazzled by your language skills. :)