I am a Muslim student in France. I have problems in doing my prayers in their times.I have no where to pray, I am far from home, and sometimes I am obliged to do all the four prayers when I return home after Isha time (I said 4 because there is no problem with fajr time).So, I have found a solution: I do my prayers sitting on my chair and I do Ruku and Sujud by moving my head (I pass all the day at a research laboratory behind my Pc at my desk, and for your information I am not alone in this room, there is other non-Muslim people. So I do that, without attracting their attention).Please tell me what do you think about it, and you can answer me in Arabic, I can read Arabic character on my Pc but I can't write in Arabic).WA JAZAKOM ALLAHO KHAIRAN.

Praise be to Allah, the Lord of the Worlds; and may His blessings and peace be upon our Prophet Muhammad and upon all his Family and Companions.

Allah has ordered Muslims to adhere to the mandatory prayers in their fixed times. Allah says: {Guard strictly (five obligatory) AsSalawât (the prayers) especially the middle Salât (i.e. the best prayer 'Asr). And stand before Allâh with obedience [and do not speak to others during the Salât (prayers)].} [2:238]
Allah says: {…..Verily, the prayer is enjoined on the believers at fixed hours.} [4:102]
Allah says: {So woe unto those performers of Salât (prayers) (hypocrites), Who delay their Salât (prayer) from their stated fixed times} [107:4,5]
So, the Muslim must adhere to the prayers in their fixed times. So, he should hasten to perform the prayer as soon as it becomes due. He should not delay the prayer from its fixed time. The Prophet (Sallallahu Alaihi wa Sallam) said: "And the earth was made a mosque for me. So, the person should pray wherever he is whenever the time of the prayer comes." [ Al-Bukhari and Muslim ]
Now, if you cannot pray in congregation, pray individually in your work or study place. But never delay the prayers from their fixed times. Know, may Allah guide you to the right path, that you should not feel any shyness while performing your Islamic rites in front of the disbelievers. Allah says to his Prophet: { Therefore proclaim openly (Allâh's Message Islâmic Monotheism) that which you are commanded, ……} [15:94]
Allah also says: {And who is better in speech than he who [says: "My Lord is Allâh (believes in His Oneness)," and then stands straight (acts upon His Order), and] invites (men) to Allâh's (Islâmic Monotheism), and does righteous deeds, and says: "I am one of the Muslims."} [41:33]
As for the prayer in the way you described, it is unlawful if you can stand up, bow down and prostrate unless there is a dire necessity for that such as fearing for your life or fear of incuring a very harmful punishment like being jailed or beaten strongly. Under such dire necessity, you can pray in the way you described but you must leave this place where you can't show your religion rites. Allah says: {Verily! As for those whom the angels take (in death) while they are wronging themselves (as they stayed among the disbelievers even though emigration was obligatory for them), they (angels) say (to them): "In what (condition) were you?" They reply: "We were weak and oppressed on earth." They (angels) say: "Was not the earth of Allâh spacious enough for you to emigrate therein?" Such men will find their abode in Hell - What an evil destination!} [4:97]
Allah knows best.