Definitely Allah forgives all sins and His mercy extends to you and to all His creatures. He said in the Qur’an, “Say, O My servants who have transgressed against themselves [by sinning], do not despair of the mercy of Allah. Indeed, Allah forgives all sins. Indeed, it is He who is the Forgiving, the Merciful.” (Az-Zumar 39:53)

Abu Hurairah (May Allah be pleased with him) reported: The Prophet (peace be upon him) said, “Allah, the Exalted, and Glorious said: ‘A slave committed a sin and he said: O Allah, forgive my sin,’ and Allah said: ‘My slave committed a sin and then he realized that he has a Rubb Who forgives the sins and punishes for the sin.’ He then again committed a sin and said: ‘My Rubb, forgive my sin,’ and Allah said: ‘My slave committed a sin and then realized that he has a Rubb Who forgives his sin and punishes for the sin.’ He again committed a sin and said: ‘My Rubb, forgive my sin,’ and Allah said: ‘My slave has committed a sin and then realized that he has a Rubb Who forgives the sin or takes (him) to account for sin. I have granted forgiveness to my slave. Let him do whatever he likes”. (Muslim)

You must first and foremost make a sincere repentance to your Lord.

You do not have to recite shahadah again but you have to repent your sins and increase making supererogatory prayers which may make up some of the salahs you missed in the past. In order to gain forgiveness, scholars have stated that the following conditions must be met:
1. Giving up of the sin itself.
2. Remorse over what has been committed.
3. A resolve not to repeat it

4- Compensating those who have been wronged or obtaining their forgiveness.

One who abandons prayers may one of two cases; 1. one who believes it is obligatory but he neglects it out of laziness, or 2. he denies its legislation. For the latter, he is a disbeliever by the consensus of all Muslim scholars. Such is the case of whoever denies a matter from the religion that a Muslim cannot be ignorant about such as fasting, Hajj and zakah.

Scholars differed on the state of the one who deliberately neglects prayers. Some scholars considered him a kafir. They have further differed on how many prayers that may render him a disbeliever. Some of them maintained that it is one salah while others stated that he must have abandoned prayers completely in order to be held a kafir. The latter view is preferred because it is based on sound evidences from the Qur’an and Hadith. In both cases, one has to repent his complete abandonment or partial negligence of prayer.

According to the view that we prefer, all your good deeds are expected and hoped to be counted for you by the mercy and blessings of Allah, since you were acting upon an act of disbelief like fornication and theft but you have not got out completely of the fold of Islam. There is a difference between the two cases.

It was narrated from Abu Hurairah that the Messenger of Allah said: “No one who commits Zina is a believer at the moment when he is committing Zina; no one who steals is a believe at the moment when he is stealing; no one who drinks wine is a believer scat the moment when he is drinking it; and no robber is a believer at the moment when he is robbing and the people are looking on.” (Al-Bukhari, Muslim, An-Nasa’i)  This is the version of Nasaa’i.

According to this hadith a Muslim on committing zina he did not get out of the fold of Islam though the hadith stated that the is not a believer at that time of committing this sin. Though iman is lifted by committing those sins, its origin and essence still exist. This is the view of the majority of scholars.

Almighty Allah knows best.