If you are interested in having continuing sexual relations with this girl, avoid all masturbation and use of pornography so that your sexual energy will build up. Then when you meet up, your interest will hopefully lead to better erections. Also, after two years, you may have some performance anxiety for the first time or so until you get more at ease with the situation.
If you put too much attention on your partner during foreplay, your brain won't receive enough arousing signals. This is what causes you to a) not get an erection b) only get a semi-hard erection c) lose your erection hardness. To stay hard and in control of ejaculation during sexual activity, you need to balance your sexual focus so your brain receives the correct balance of arousing signals.