failing to do full reps on certain exercises

Hello guys, so now I finally managed to get going and work out consistently (currently I've been doing it for 2 weeks) at home with a barbell currently I noticed that particularly when trying to do lunges I cannot complete the sets not even without the barbell.

Would it ok if I cannot complete the sets or would you suggest me to do something else in order to gain the strength to do them?

As well if you could share some YouTube that teaches how to have an integral work out only with a barbell would be great.

Thanks.