MB 9: The first verse - In order to accept upon oneself the yoke of the Kingdom of Heaven [which is what the first verse entails] at the time for reading the Shema, and he should try and learn a Law which mentions the Exodus from Egypt in order to mention the Exodus from Egypt [which is mentioned in the third paragraph of the Shema] at the time for reading the Shema. After his learning it is good if he completes the whole of the Shema, even if its time has passed.
MB 10: He should not interrupt at all - He means to say that even for the first verse [he should not interrupt] and even if he is learning on his own. The Later Rabbis wrote that even if he started learning when it was forbidden to do so, namely after the time for reading the Shema and saying the Amidah had arrived when it would have been forbidden for him to start learning without first having prayed, if he is learning at home and he doesn't usually go to Shul to pray, as written in Siman 89, nevertheless if had already started [learning] he does not have to interrupt and he is permitted to learn for as long as there is still time [to say the Shema and the Amidah]. In the Eliyahu Rabba he decides that in regard to the reading of the Shema, which is [a Mitzvah] from the Torah, even if there remains enough time afterwards to read it, nevertheless he is required to interrupt [his learning] immediately and read all of it if he is learning on his own, see there in Siman 70 and in this Siman. But all this is if he were learning at home, but if he is learning in the House of Study [Beis Medrash], or even at home but he started learning when it was permitted to do so, namely before the time for reading the Shema had arrived, then definitely one may rely on the opinion of the Rema that he should not interrupt, even afterwards, for so long as there is time [still to read the Shema], and see in the Biur Halacha.