The flowers
Lilies carry the traditional weight of mourning, and white or cream is the safe register. A lotus adds calm. Avoid red, avoid celebration, avoid a large showy arrangement — this is not a moment for volume.
Two stems is plenty. Restraint reads as respect here.
What not to write
Do not explain the death. Do not say it was for the best, or that they are in a better place, or that you know how they feel. Even if you have been through something similar, the sentence “I know how you feel” takes the moment away from them.
Do not ask what you can do. It puts a task on someone who has no capacity for tasks.
What to write instead
Name the person who died, if you knew them. “She was the one who always asked about my mum” is worth more than any condolence formula.
Then say what you are actually offering, specifically: “I will bring food on Thursday and leave it at the door.” Or, if you cannot offer something concrete, keep it to presence: “I am thinking about you, and I am not going anywhere.”
And come back in a month. The link still works, and a second message in week four will matter more than the first one did.