Game against (much) stronger opponent

[PROVOK3]

In case its not obvious, I'm the black one.

Now that I can't play BaToo anymore, I have gotten back to playing Go. Almost on a daily basis, however, a much stronger opponent offers me a no handicap game. I have a lots of difficulty trying to match this player, who I am not sure could be playing seriously or a teaching game. Regardless, my opening moves are very weak, and my opponent is really good at invading and reducing my territory. I need to have a stronger opening game and better responses to invasions and reductions. Aside from the many mid-game errors that I commit, could anyone give me some tips on how to improve my opening game?

[EdLee]

9: Try S5 instead.
21: You are in atari. Connect at P6, then White's R7 group only has 3 liberties. Study the resulting capture race.

Work on seeing ataris, be aware of liberties, and try to read a few more moves ahead.

[Joaz Banbeck]

Think 'connect your stones; disconnect his', and get a copy of "38 Basic Josekis".

[Dusk Eagle]

I don't know how necessary it is to get a copy of "38 basic joseki". If you're going to spend money on books, I think there are more important subjects than that. If you want to learn some joseki, at your level eidogo.com might be best. However, I think most of your problems weren't as much about joseki errors as they were about basic principles, so that's what I've mainly addressed here: