1) If one has chummus (thick) tahini (liquidy) and matbucha (chunky) on a plate can one mix them as one eats them or prepaes to put them on bread? Or is this losh?
2) Can one, before shabbat, add water into a oil light to raise the level of the flame?
3) Is it lason hara to discuss a teacher at school with other students if the teacher is jewish?
Answer:
1) The prohibition of lash applies to particles that are joined together by liquid. In this case, I do not see that there are particles that will be joined together, and therefore do not see a case of lash. If the matbucha is chunky, as you write, it is hard to believe that a paste or dough of any consistency will result. No prohibition will therefore be involved.
See https://dinonline.org/2011/06/23/preparing-tehina-on-shabbos/ for a discussion of preparing tahini sauce on Shabbos. For mixing big pieces, see also the Mishnah Berurah 321:68, and the Shemiras Shabbos Kehilchasa 8:4.
Concerning mixing tahini with humus, this is mixing two pastes of different consistencies, and because no pieces are involved, there appears to be no prohibition. This is the assumption made by Shut Or Yitzchak (Orach Chaim 175); see also The Shabbos Kitchen, p. 163.
2) I do not see any problem in doing this before Shabbos. Of course, one must be careful not to extinguish the Shabbos candle over which the berachah was made.
3) This could be lashon hara, depending on the nature of the conversation, the purpose of the conversation, whether this purpose can be achieved by other means, and so on. The principles of lashon hara, as set out by the Chafetz Chaim, should be consulted (or re-submit with more specifics).
Best wishes.
