I read the quote below from a website and I'd like to know if I have a valid excuse to not pray. I have never, as I remember, completely read and understood the Quran in my language (English). I have other issues in my life as well, but would this be a good enough reason to miss Salat?
"We are informed that one will be punished in the Hell for 70,000 years for one "Salat" prayer which is not performed due to laziness and without any excuse." (http://www.hizmetbooks.org/Ethics_of_Islam/e1-35.html)

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 prayers are the greatest pillar of Islam after the two witnesses i.e. giving testimony that none has the right to be worshipped but Allaah and that Muhammad is His messenger. It is the most important matter in the life of a Muslim. We have issued Fatwa: 88132 about its importance in Islam, and Fataawa: 84390 and 87319 about the ruling of the one who abandons prayers. As long as a person is mature and sane, there is no excuse that justifies giving up prayers. Allaah did not drop the duty of performing prayers from those who fight for the sake of Allaah while in the battlefield. Allaah Says (which means): {And when you travel throughout the land, there is no blame upon you for shortening the prayer, [especially] if you fear that those who disbelieve may disrupt [or attack] you. Indeed, the disbelievers are ever to you a clear enemy. And when you [i.e. the commander of an army] are among them and lead them in prayer, let a group of them stand [in prayer] with you and let them carry their arms. And when they have prostrated, let them be [in position] behind you and have the other group come forward which has not [yet] prayed and let them pray with you, taking precaution and carrying their arms. Those who disbelieve wish that you would neglect your weapons and your baggage so they could come down upon you in one [single] attack.}[Quran 4: 102].

The verses continue {remember Allaah standing, sitting, or [lying] on your sides. But when you become secure, re-establish [regular] prayer. Indeed, prayer has been decreed upon the believers a decree of specified times.} [Quran 4:103] The companions were not exempted from performing prayers even though they were fighting the enemy.

The Prophet said to 'Imraan Bin Husayn when he was suffering from piles: "Pray while standing, if unable, then sitting, if yet unable, then lying on your side." [Al-Bukhari]  The prayers were not dropped even from a patient.

Dear brother, now you may know through the given details that the duty of performing prayers does not drop from an adult and sane person. You have to give precedence to this matter over all other matters. Memorizing the whole Quran or understanding it is not a stipulation for performing prayers. But you have to recite the chapter Al-Faatihah as mentioned in the where the Prophet said: "The prayer of the one who does not recite Al-Faatihah is invalid." If you are performing prayer as a follower (i.e. with the congregation) then reciting Al-Faatihah is not compulsory, according to the majority of the Muslim scholars.

In short, a Muslim must never abandon his prayers nor neglect them since negligence in this matter is among the characteristics of hypocrites.  Allaah Says (which means): {When they stand for prayer, they stand lazily, showing [themselves to] the people and not remembering Allaah except a little,}[Quran 4:142].

Finally, the site you are asking about contains falseness and the matters that contradict to the true belief of Ahlus-Sunnah Wal-Jamaa'ah. So, we advise you not to visit it again for the sake of your faith and religion.

Allaah Knows best.