if someone could take a moment to briefly explain these problems for me
1. why at the end of the conversation of borer does lealtar get accepted without a matkif while previously when attempting to answer that it was bo bayom the gemarah questioned that one cant do baking for even bo bayom,.Why isnt a similar qustion raised for lealter?
2. acc to rambam why isnt one chayav twice for cooking , does he view both softening and hardening as melacha
3. how did the gemarah say zoreah and netiyah are av melachot, arent there only 39?
if possible short simple answers to clarify peshat for me would be much appreciated
1) "L'Altar" means for the meal that one is eating (or about to eat), as Rabeinu Chananel explains (see end of Insights). It follows then that doing Borer for immediate use is the normal manner of eating and is therefore permitted. Doing Borer for use later on in the day is not considered the normal manner of eating and is therefore prohibited. Cooking, though, is always forbidden, and doing it in the normal manner of eating makes no difference. Thus, doing Borer for immediate use is not comparable to cooking, while doing Borer for use later is comparable to cooking.
2) You are apparently referring to the Gemara on 74b, which says that one is Chayav for Bishul for heating tar. We might have thought that one is Patur since the tar becomes hard when it cools; therefore the Gemara needed to teach that one is nevertheless Chayav for cooking. The softening process and hardening process are not separate Melachos. What indication is there in the Rambam that would lead us to think that one should be Chayav twice for cooking?
3) There are 39 Avos with regard to separate Korbanos (Chata'os). One who does both Zore'a and Note'a is Chayav only one Chatas. Both acts are called Avos because they are the same Av; they are merely describing the action done with different objects (see Background section). This seems to be the intention of RASHI. The RITVA explains that Rashi would maintain that one would indeed be Chayav to bring two Korbanos, one for Zomer and one for Zore'a, and he challenges Rashi and gives another explanation of the Gemara.