Terumot & Ma’aserot

There is a guava tree in my apartment building’s shared courtyard (with 15 families). Every week I pick two to four fruits and take them home. Am I supposed to take terumot and ma’aserot from the guava with a blessing? If the tree was in a public playground, would its fruit also be subject to terumot and ma’aserot?

I grow herbs (thyme, rosemary, basil, etc.) and use them as seasoning. We actually eat them; they don’t only provide a flavor. How am I supposed to go about taking terumot and ma’aserot from them? Each time I pick a small bunch of leaves, so I would set aside less than a leaf? For example: how much am I supposed to take from the 2-3 basil leaves that I add to the spaghetti sauce?