I relly need a dating advice for my problem?

I have a dumb problem, you see i'm an 18 year old guy from europe. Lately i have been talking to girls, you know i'm at that age and all. I think i'm getting a hang of it, the problem that i usually face is that when im actually get a girl's number and i text dem it always feels like they are rejecting me.

for example i met a girl on the buss on my way home and we talked for about 5 min, i got her number and it felt like everything went well, so i texted her thiss after about 4 hours

me - Hi, it's me (name) the guy from the buss. i am free this weekend so if you wanna hang message me

she replies 2 hours after

her - hi fun to hear from you, this weekend i can't my sister is coming over for a visit, maybe some other time maybe.

In the text she mensches that she is happy to hear from me which is a positive thing then she says maybe another time. The many is what concerns me because it wasn't a question. Am i overthinking or am i right about being rejected.

Ps just wanna improve my dating skills