Can You Pray Tarawih without Praying Isha?
Question

If a person misses ‘Isha prayer, it may be noted in the month of Ramadan in particular – as you are well aware – that there are more than two jama‘ahs in the same place and at the same time. This is something that often happens at the time of ‘Isha and Tarawih prayer. 
For example, when the first jama'ah has finished ‘Isha prayer, another jama‘ah comes and they say the iqamah (call immediately preceding the prayer) and they begin to pray ‘Isha. During this time, the first jama'ah gets up and starts to pray Tarawih. 
Is it permissible to have two jama‘ahs at the same time and in the same place? What is your advice – may Allah preserve you and bless your work – to imams and those who come late to ‘Isha prayer? 
Is it permissible for me to pray with the imam having the intention of ‘Isha whilst he has the intention of Tarawih?
Praise be to Allah.Importance of offering prayers on time
The Muslim should hasten to do good deeds and compete with others in doing acts of worship, and this is emphasized even more during the month of Ramadan, in which the gates of Paradise are opened and the gates of Hell are closed, the devils are chained up and a caller calls out every night: O seeker of good, advance; O seeker of evil, go back. 
Our advice to the one who misses some of the prayers without any excuse, or misses them because of something haram, such as those who neglect the prayer in order to watch soap operas, is that they should be keen to offer the prayers with the Muslims and they should hasten to pray when they hear the adhan (call to prayer). Ramadan is a month of worship and multiple rewards; we ask Allah to protect us from the evil of our own selves and to help us to obey and worship Him, for He is the Most Munificent, Most Generous. 
Can you pray ‘Isha with tarawih?
If some people have missed ‘Isha prayer with the regular imam, should they pray ‘Isha in congregation (jama‘ah), or should they join the imam in Tarawih prayer, with the intention of praying ‘Isha? That depends on their situation: 
If they came in straight after the prayer, and there is enough time before Tarawih to pray ‘Isha, then in this case it is better for them to pray in jama'ah on their own, so as to avoid differing with those scholars who do not allow a person to offer an obligatory prayer behind (an imam) who is offering a nafl prayer. 
But if they came in whilst Tarawih prayer was in progress, or the imam started to pray Tarawih shortly after ‘Isha, and there is the fear that if a second jama'ah prays, the two groups will disturb one another, then in this case it is better to join the imam in Tarawih, with the intention of praying ‘Isha. Then when the imam says the taslim after two rak‘ahs, they should stand up and complete the prayer by themselves. 
Shaykh Ibn Baz (may Allah have mercy on him) was asked: We notice that in some mosques, those who come after the end of ‘Isha prayer and the beginning of Tarawih offer a second [‘Isha] prayer, but by doing so they disturb those who are praying Tarawih. Is it better for them to offer the prayer in jama'ah, or to join the imam in Tarawih prayer, with the intention of ‘Isha? Is the ruling different if it is one person or a group that comes in? 
He replied: 
“If those who come in are two or more, then it is better for them to offer the prayer on their own – i.e., ‘Isha prayer – then to join the people in Tarawih. But if they join the imam with the intention of praying ‘Isha, then when the imam says the taslim, each of them gets up and completes the prayer by himself, there is nothing wrong with that, because it was proven from Mu‘adh (may Allah be pleased with him) that he used to pray the obligatory prayer of ‘Isha with the Prophet (blessings and peace of Allah be upon him), then he would go back to his people and lead them in offering that prayer; for him it was nafl but for them it was obligatory. But if only one person comes in, then it is better for him to join the imam with the intention of ‘Isha, so that he will attain the virtue of praying in jama'ah. Then when the imam says the taslim following two rak‘ahs, he should complete ‘Isha by himself . May Allah help us all to understand Islam properly.” (Majmu‘ Fatawa Ibn Baz, 30/30) 
And Allah knows best.