1. Diagram seems to be fine. However we don't see pin numbering on LCD. Sometimes pins are like: 15 16 1 2 3 4 ... 14 (at least pin 1 is usualy marked).

2. Library should take care of inputs/inputs. So you can remove pinModes for them. Also change variables to constant variables and use them for lcd initialization: LiquidCrystal lcd(rs, enable, d4, d5, d6, d7);

3. Potenciometter in diagram is contrast setting. You have to preset correct value for it. Start with everything is black and find value where this black is almost invisible. If you've something displayed on lcd, it would be even easier to find right position as text just shows up.

Edit: I've just tested it and it's working fine. With the same wiring and contrast pot adjusted to the right position

1. Diagram seems to be fine. However we don't see pin numbering on LCD. Sometimes pins are like: 15 16 1 2 3 4 ... 14 (at least pin 1 is usualy marked).

2. Library should take care of inputs or outputs. So you can remove pinModes for them. Also change variables to constant variables and use them for lcd initialization: LiquidCrystal lcd(rs, enable, d4, d5, d6, d7);

3. Potentiometer in diagram is contrast setting. You have to preset correct value for it. Start with everything is black and find value where this black is almost invisible. If you've something displayed on LCD, it would be even easier to find right position as text just shows up.

Edit: I've just tested it and it's working fine. With the same wiring and contrast pot adjusted to the right position

1. Diagram seems to be fine. However we don't see pin numbering on LCD. Sometimes pins are like: 15 16 1 2 3 4 ... 14 (at least pin 1 is usualy marked).

2. Library should take care of inputs/inputs. So you can remove pinModes for them. Also change variables to constant variables and use them for lcd initialization: LiquidCrystal lcd(rs, enable, d4, d5, d6, d7);

3. Potenciometter in diagram is contrast setting. You have to preset correct value for it. Start with everything is black and find value where this black is almost invisible. If you've something displayed on lcd, it would be even easier to find right position as text just shows up.

1. Diagram seems to be fine. However we don't see pin numbering on LCD. Sometimes pins are like: 15 16 1 2 3 4 ... 14 (at least pin 1 is usualy marked).

2. Library should take care of inputs/inputs. So you can remove pinModes for them. Also change variables to constant variables and use them for lcd initialization: LiquidCrystal lcd(rs, enable, d4, d5, d6, d7);

3. Potenciometter in diagram is contrast setting. You have to preset correct value for it. Start with everything is black and find value where this black is almost invisible. If you've something displayed on lcd, it would be even easier to find right position as text just shows up.

Edit: I've just tested it and it's working fine. With the same wiring and contrast pot adjusted to the right position