I know a religious girl and promised her that I will marry her in the future, because I am short of money right now. I give her recorded Islamic lessons and do not talk with her a lot. What is the viewpoint of Sharee‘ah in this case?
May Allaah Reward you.

All perfect praise be to Allaah, The Lord of the Worlds. I testify that there is none worthy of worship except Allaah, and that Muhammad, sallallaahu ‘alayhi wa sallam, is His Slave and Messenger.

The relationship between men and women is not permitted unless within the frame of marriage approved by Sharee‘ah. Neither man nor woman is permitted to talk to the other sex unless there is a need. In your question, there is no valid need under Sharee‘ah to talk with her. However, the tapes can be exchanged through a reliable woman without outraging the boundaries of Allaah such as meeting her or chatting with her. Even if there is no trusted woman to do the job, it is still impermissible for you to give her the tapes. This is a means that may lead to falling into sinning, based on the well-known jurisprudential rule:  “Warding off harm has precedence over bringing about interests.” Therefore, you have to forsake such a girl and beware of this relationship. Allaah The Almighty Says (what means): {O you who have believed, do not follow the footsteps of Satan. And whoever follows the footsteps of Satan – indeed, he enjoins immorality and wrongdoing.} [Quran 24:21] Because of Satan’s scheming, he does not command the person to commit adultery directly, rather, he insinuates him/her step by step, until the person falls in it. The temptation of women is one of the greatest trials that face Muslim men. The Prophet said: “I did not leave a more harmful temptation to men behind me than the temptation of women.” [Al Bukhari and Muslim] The Prophet said: “Beware of this life and women, for the first thing the children of Israel have been tried with was women.” [Muslim]

Many righteous early Muslims gave advice and warned of Fitnah of women. Mu‘aath ibn Jabal said, “What I fear most for you is the Fitnah of women.” [Al-Bayhaqi]

Sa‘eed bin Al-Musayyib also said, “Satan never despairs of someone but overcomes him by means of women.” [Ath-Thahabi] This indicates the danger of this relation.

We bring the fact that the phrase, “What is the viewpoint of Sharee‘ah in such and such?” is not correct to the asker’s attention. Instead, he should say, “What is the ruling of Sharee‘ah in such and such?” because it is possible that one's viewpoint may be correct or not – a case which is not applicable to the rulings, commands and forbiddances of the Islamic Sharee’ah.

Allaah Knows best.