A few notes (no pun intended) that may (or may not) help...
Tempo is just the speed in beats per minute at which you play. Don't sweat that, you can play at whatever speed you want - or at least until your fingers refuse to go faster!
Rhythm is the tricky bit, but it gets easier the more time and concentration you put in.
A couple of things that might help when you're working on strumming patterns:
Step 1) Establish whether a tune is in
4/4 or
3/4. Most will be in one or the other, with the majority being in 4/4. If it's in 4/4 (AKA
common time), then a count of "
1 2 3 4
1 2 3 4" should fit over it. If it's in 3/4 (AKA
waltz time), then a count of "
1 2 3
1 2 3" will fit.
Step 2) Practise strumming a straight
up-down-up-down with a down-stroke on every count. Count in your mind, or out loud, and say "
and" for the upstrokes.
Your strumming should be like one of these depending on the time signature or the song - 4/4 or 3/4. The examples show two measures (bars) of each time sig:
Code:
1 & 2 & 3 & 4 & | 1 & 2 & 3 & 4 &
D U D U D U D U | D U D U D U D U (4/4)
1 & 2 & 3 & | 1 & 2 & 3 &
D U D U D U | D U D U D U (3/4)
Many instructors on videos will keep that steady up-down-up-down motion going steady through the song no matter what. So, even where they don't strum a count beat or an "and" beat they will still "mime" that beat in the strum, just without actually brushing the strings. Once you get that steady, uninterrupted up-down-up-down strum thing into your head and your fingers it can make it easier to figure out the patterns people are playing - because, as often as not, if you follow the pattern played by the instructor you will find your hand is usually in the right place for whichever up or down stroke is required.
Step 3) Get some paper and a pencil!
Write down that 1 & 2 & 3 & 4 & or 1 & 2 & 3 & count pattern for whatever time the song is in, then as you work through the song on the video write the U or D or X/chunk (or whatever notation you use) under or over the count pattern. That way you can see exactly where the strum pattern fits into the count of the bar.
As has been said, strum patterns just come naturally after a while - but to get to the stage where they do come naturally it is helpful to learn and practise as many of the ones people have already used as possible. If nothing else it shows you some options you might otherwise miss. The transition between learning strums "parrot fashion" and ad-libbing them without thinking just happens gradually. You just start to find yourself doing your own thing ... and it working!
Good luck! :shaka: