My question is that I ejaculated and got in the state of janaba and after that I ejaculated one more time while I was in the state of janaba do I need to take only one ghusl to get out of major impurity?
The idea of ghusl is being in a pure state in order to pray, you can have multiple intercourse and can do ghusl after them in order to pray.
The point is once there's a penetration ghusl (not necessary ejaculation! hadd in case of zina for more information read How deep does the penis need to be inside before it's classed as zina and is subject to the hadd punishment?) is necessary this is agreed upon among all scholars. Further ghusl is necessary in case of ejaculation or legal (or illegal) intercourse or wet dreams for a person who is alive. How many times you perform ghusl is up to you (once is necessary and would be sufficient if you won't miss any prayer), your piety and the time necessary to perform ghusl to pray your next prayer on time. As else delaying ghusl would be sinful!
Further the prophet () used to perform wudu' between two acts of intercourse:
The Messenger of Allah (ﷺ) said: When anyone amongst you has sexual intercourse with his wife and then he intends to repeat it, he should perform ablution. In the hadith transmitted by Abu Bakr. (the words are):" Between the two (acts) there should be an ablution," or he (the narrator) said:" Then he intended that it should be repeated." (Sahih Muslim)
See also How to do ghusl of janabat and hayd? (which also come to the conclusion that if 2 reasons for ghusl coincide one ghusl is necessary and sufficient)