How can you tell if your online partner is serious or not?

From this online dating site called Peru Women, I was able to match with a number of women from around the world. But there’s always this one thing that bothers me when striking up conversations with them –are they serious or not? I’m still quite new with everything that has to do with dating someone from the internet and I’m very dense when it comes to communicating online.
Unlike talking to someone in person, I can’t see their facial expressions or hear the tone of their voice through chat. This is a problem for me, especially when I take interest in a certain woman. I can’t seem to push through with a potential romantic relationship with someone because I’m always worried that she may not be serious with me.

There are some matches that I invested my time in and whenever it reaches to about a week of constant communication, I start feeling anxious. How can you tell if your online partner is serious with you or not? I find it hard to understand if things are going great or if they might to choose to stop communicating with me at the last minute.
I just want to make sure that I won’t make any wrong decisions and to avoid wasting my time with someone. I’m trying this type of dating for a reason and it’s to build a relationship with a woman I’m interested in. I’ve had multiple relationships in the past and they never seem to work out.
Please folks, I need advice on this to put my mind at ease and to boost my confidence as well. Any tips or advice will surely be helpful for me! Help please!!!