What do you suggest if i struggle to get and keep and erection while standing up, is this normal?

Yes, can be ...: As we age, inevitably, the coordination between circulatory and nerve systems slowly changes, deteriorates, and becomes more functionally marginal. Such pace may vary among people. So, at 47, you may become less functional in standing than in lying position, especially after eating a lot to a full stomach, but healthy lifestyle may slow down such realistic life process.