Are you asking if you can leave?
You cannot just stop paying rent.
At least, you can of course. But if you do then the landlady would have grounds to seek your eviction.
She may do that anyway if she has served a S21 notice upon you.
It is quite difficult to tell really what is the specific complaint here. You describe a delay in repairs but then say that they are done now. If they are done then the issue falls away.
You cannot force her to renew with you. If the S21 notice is valid and in time then she can rely on that and that would mean the agreement comes to an end in July. Although if you were to refuse to go then she would need a court order to get you out but it can be done.
Can I clarify anything for you?
Yes, she can rely on the S21 notice. She doesn't need to get you to sign it at all. She just needs to serve it on you.
Nails on the floor per se would not amount to disrepair.
If there are nails on the floor then they can be removed?
All the best.