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 is His slave and Messenger. We ask Allaah to exalt his mention as well as that of his family and all his companions.
The fact that your wife is slow in ejaculating when having sexual intercourse may be due to a disease that requires consulting some specialist doctors. It might also be due to you ejaculating quickly, or due to the lack of foreplay before sexual intercourse which normally leads to sexual satisfaction during intercourse. So you have to find out the reason so that you will treat the problem accordingly. As regards putting your hand in your wife's vagina so that she would get pleasure, this is permissible in principle. However, you should avoid it and only rely on sexual intercourse because your wife could be accustomed to it, and this could lead her to masturbate with her hand, and this is something which is forbidden.
Allaah knows best.