1. All sins can be forgiven if repented to sincerely. Long as we live, we have opportunity to repent.
2. Oaths or swearing should done by Allah's name only.
3. Don't be willy nilly making promises left and right
Making a promise to Allaah is a kind of vow and an oath (yameen).
Allaah says (interpretation of the meaning):
“And of them are some who made a covenant with Allaah (saying): ‘If He bestowed on us of His Bounty, we will verily, give Sadaqah (Zakaah and voluntary charity in Allaah’s Cause) and will be certainly among those who are righteous’”
[al-Tawbah 9:75]
Al-Zuhri (may Allaah have mercy on him) said: Whoever makes a promise to Allaah and breaks it, let him give in charity that which Allaah has enjoined in the case of a broken oath.
Shaykh al-Islam [Ibn Taymiyah] said in
al-Ikhtiyaaraat (pp 562-563):
If a person says, “I promise Allaah that I will perform Hajj this year,” then this is a vow, a promise and an oath (yameen). End quote.
haykh al-Islam said in
al-Ikhtiyaaraat (pp. 562-563):
Whoever repeats an oath before offering expiation, the correct view is that if this oath had to do with one action, only one expiation is to be offered; otherwise he must offer two. End quote.
The expiation for breaking an oath is to set free a slave, or to feed or clothe ten poor persons. Whoever cannot do any of those things should fast for three days, because Allaah says (interpretation of the meaning):
“Allaah will not punish you for what is unintentional in your oaths, but He will punish you for your deliberate oaths; for its expiation (a deliberate oath) feed ten Masaakeen (poor persons), on a scale of the average of that with which you feed your own families, or clothe them or manumit a slave. But whosoever cannot afford (that), then he should fast for three days. That is the expiation for the oaths when you have sworn. And protect your oaths (i.e. do not swear much). Thus Allaah makes clear to you His Ayaat (proofs, evidences, verses, lessons, signs, revelations, etc.) that you may be grateful”
[al-Maa'idah 5:89]
https://islamqa.info/en/38934